536:– Several SMTP commands are allowed to be placed in one network packet and "pipelined". For example, if an email is sent with a CC: header, several SMTP "RCPT TO" commands might be placed in a single packet instead of one packet per "RCPT TO" command. The SMTP protocol, however, requires that errors be checked and everything is synchronized at certain points. Many spammers will send everything in a single packet since they do not care about errors and it is more efficient. Some MTAs will detect this invalid pipelining and reject email sent this way.
862:
facility. Depending on the server and internet speed, a tarpit can slow an attack by a factor of around 500. Many systems will simply disconnect if the server doesn't respond quickly, which will eliminate the spam. However, a few legitimate email systems will also not deal correctly with these delays. The fundamental idea is to slow the attack so that the perpetrator has to waste time without any significant success.
777:" is placed in the source HTML of a web site in a way that it isn't displayed on the web page, human visitors to the website would not see it. Spammers, on the other hand, use web page scrapers and bots to harvest email addresses from HTML source code - so they would find this address. When the spammer later sends to the address the spamtrap knows this is highly likely to be a spammer and can take appropriate action.
587:, Policyd-weight and others use some or all of the various tests for spam, and assign a numerical score to each test. Each message is scanned for these patterns, and the applicable scores tallied up. If the total is above a fixed value, the message is rejected or flagged as spam. By ensuring that no single spam test by itself can flag a message as spam, the false positive rate can be greatly reduced.
970:'s ezmlm) support "confirmed opt-in" by default. Whenever an email address is presented for subscription to the list, the software will send a confirmation message to that address. The confirmation message contains no advertising content, so it is not construed to be spam itself, and the address is not added to the live mail list unless the recipient responds to the confirmation message.
43:
557:– An SMTP connection should always be closed with a QUIT command. Many spammers skip this step because their spam has already been sent and taking the time to properly close the connection takes time and bandwidth. Some MTAs are capable of detecting whether or not the connection is closed correctly and use this as a measure of how trustworthy the other system is.
1105:
an email address. The SMTP server must check if the email address in the FROM field of an outgoing message is the same address that belongs to the user's credentials, supplied for SMTP authentication. If the FROM field is forged, an SMTP error will be returned to the email client (e.g. "You do not own the email address you are trying to send from").
1104:
Both malicious software and human spam senders often use forged FROM addresses when sending spam messages. Control may be enforced on SMTP servers to ensure senders can only use their correct email address in the FROM field of outgoing messages. In an email users database each user has a record with
499:
protocol allows for temporary rejection of incoming messages. Greylisting temporarily rejects all messages from unknown senders or mail servers – using the standard 4xx error codes. All compliant MTAs will proceed to retry delivery later, but many spammers and spambots will not. The downside is that
1375:
We do not tolerate the transmission of spam. We monitor all traffic to and from our web servers for indications of spamming and maintain a spam abuse complaint center to register allegations of spam abuse. Customers suspected to be using our products and services for the purpose of sending spam are
312:
There are now a large number of applications, appliances, services, and software systems that email administrators can use to reduce the load of spam on their systems and mailboxes. In general these attempt to reject (or "block"), the majority of spam email outright at the SMTP connection stage. If
272:
Systems that use "ham passwords" ask unrecognised senders to include in their email a password that demonstrates that the email message is a "ham" (not spam) message. Typically the email address and ham password would be described on a web page, and the ham password would be included in the subject
259:
email address — an address which the user can disable or abandon which forwards email to a real account. A number of services provide disposable address forwarding. Addresses can be manually disabled, can expire after a given time interval, or can expire after a certain number of messages have been
193:
A common piece of advice is to not to reply to spam messages as spammers may simply regard responses as confirmation that an email address is valid. Similarly, many spam messages contain web links or addresses which the user is directed to follow to be removed from the spammer's mailing list – and
865:
An organization can successfully deploy a tarpit if it is able to define the range of addresses, protocols, and ports for deception. The process involves a router passing the supported traffic to the appropriate server while those sent by other contacts are sent to the tarpit. Examples of tarpits
656:
To check the domain names in the rDNS to see if they are likely from dial-up users, dynamically assigned addresses, or home-based broadband customers. Since the vast majority of email that originates from these computers is spam, many mail servers also refuse email with missing or "generic" rDNS
395:
which collects the checksums of messages that email recipients consider to be spam (some people have a button on their email client which they can click to nominate a message as being spam); if the checksum is in the database, the message is likely to be spam. To avoid being detected in this way,
202:
Businesses and individuals sometimes avoid publicising an email address by asking for contact to come via a "contact form" on a webpage – which then typically forwards the information via email. Such forms, however, are sometimes inconvenient to users, as they are not able to use their preferred
1204:
Artificial intelligence techniques can be deployed for filtering spam emails, such as artificial neural networks algorithms and
Bayesian filters. These methods use probabilistic methods to train the networks, such as examination of the concentration or frequency of words seen in the spam versus
742:
as his sender's address. If the receiving MTA tries to make the callback using the trap address in a MAIL FROM command, the receiving MTA's IP address will be blacklisted; (3) Finally, the standard VRFY and EXPN commands used to verify an address have been so exploited by spammers that few mail
571:
Another approach is simply creating an imitation MTA that gives the appearance of being an open mail relay, or an imitation TCP/IP proxy server that gives the appearance of being an open proxy. Spammers who probe systems for open relays and proxies will find such a host and attempt to send mail
410:
Some email servers expect to never communicate with particular countries from which they receive a great deal of spam. Therefore, they use country-based filtering – a technique that blocks email from certain countries. This technique is based on country of origin determined by the sender's IP
730:
Since a large percentage of spam has forged and invalid sender ("from") addresses, some spam can be detected by checking that this "from" address is valid. A mail server can try to verify the sender address by making an SMTP connection back to the mail exchanger for the address, as if it were
660:
A Forward
Confirmed reverse DNS verification can create a form of authentication that there is a valid relationship between the owner of a domain name and the owner of the network that has been given an IP address. While reliant on the DNS infrastructure, which has known vulnerabilities, this
550:
technique is simply the adding of an MX record pointing to a non-existent server as the "primary" (i.e. that with the lowest preference value) – which means that an initial mail contact will always fail. Many spam sources do not retry on failure, so the spammer will move on to the next victim;
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is any server software which intentionally responds extremely slowly to client commands. By running a tarpit which treats acceptable mail normally and known spam slowly or which appears to be an open mail relay, a site can slow down the rate at which spammers can inject messages into the mail
139:
Sharing an email address only among a limited group of correspondents is one way to limit the chance that the address will be "harvested" and targeted by spam. Similarly, when forwarding messages to a number of recipients who don't know one another, recipient addresses can be put in the
984:
Email senders typically now do the same type of anti-spam checks on email coming from their users and customers as for inward email coming from the rest of the
Internet. This protects their reputation, which could otherwise be harmed in the case of infection by spam-sending malware.
514:
says that an SMTP server "MAY verify that the domain name argument in the EHLO command actually corresponds to the IP address of the client. However, if the verification fails, the server MUST NOT refuse to accept a message on that basis." Systems can, however, be configured to
485:– A sending server is required to wait until it has received the SMTP greeting banner before it sends any data. A deliberate pause can be introduced by receiving servers to allow them to detect and deny any spam-sending applications that do not wait to receive this banner.
206:
In some cases contact forms also send the message to the email address given by the user. This allows the contact form to be used for sending spam, which may incur email deliverability problems from the site once the spam is reported and the sending IP is blacklisted.
122:
Anti-spam techniques can be broken into four broad categories: those that require actions by individuals, those that can be automated by email administrators, those that can be automated by email senders and those employed by researchers and law enforcement officials.
803:
needs, and as long as users consistently mark/tag the emails, can respond quickly to changes in spam content. Statistical filters typically also look at message headers, considering not just the content but also peculiarities of the transport mechanism of the email.
913:
There are a variety of techniques that email senders use to try to make sure that they do not send spam. Failure to control the amount of spam sent, as judged by email receivers, can often cause even legitimate email to be blocked and for the sender to be put on
1191:
Since spamming is facilitated by the fact that large volumes of email are very inexpensive to send, one proposed set of solutions would require that senders pay some cost in order to send email, making it prohibitively expensive for spammers. Anti-spam activist
429:
which allow a mail server to quickly look up the IP of an incoming mail connection - and reject it if it is listed there. Administrators can choose from scores of DNSBLs, each of which reflects different policies: some list sites known to emit spam; others list
374:
A method which may be used by internet service providers, by specialized services or enterprises to combat spam is to require unknown senders to pass various tests before their messages are delivered. These strategies are termed "challenge/response systems".
572:
through it, wasting their time and resources, and potentially, revealing information about themselves and the origin of the spam they are sending to the entity that operates the honeypot. Such a system may simply discard the spam attempts, submit them to
296:
and
Network Abuse Clearinghouse to assist, they are not always accurate. Historically, reporting spam in this way has not played a large part in abating spam, since the spammers simply move their operation to another URL, ISP or network of IP addresses.
926:
Since spammer's accounts are frequently disabled due to violations of abuse policies, they are constantly trying to create new accounts. Due to the damage done to an ISP's reputation when it is the source of spam, many ISPs and web email providers use
291:
Tracking down a spammer's ISP and reporting the offense can lead to the spammer's service being terminated and criminal prosecution. Unfortunately, it can be difficult to track down the spammer, and while there are some online tools such as
240:
or attacks upon security vulnerabilities in the HTML renderer. Mail clients which do not automatically download and display HTML, images or attachments have fewer risks, as do clients who have been configured to not display these by default.
595:
Outbound spam protection involves scanning email traffic as it exits a network, identifying spam messages and then taking an action such as blocking the message or shutting off the source of the traffic. While the primary impact of
696:
disallowed in mail messages. Thus, if a site receives spam advertising "herbal Viagra", the administrator might place this phrase in the filter configuration. The mail server would then reject any message containing the phrase.
603:
Outbound spam protection not only stops spam, but also lets system administrators track down spam sources on their network and remediate them – for example, clearing malware from machines which have become infected with a
1034:
or send email. This practice is somewhat controversial when ISPs block home users, especially if the ISPs do not allow the blocking to be turned off upon request. Email can still be sent from these computers to designated
339:
A number of systems have been developed that allow domain name owners to identify email as authorized. Many of these systems use the DNS to list sites authorized to send email on their behalf. After many other proposals,
448:
Most spam/phishing messages contain an URL that they entice victims into clicking on. Thus, a popular technique since the early 2000s consists of extracting URLs from messages and looking them up in databases such as
1007:. For this reason it is generally preferable for most rejection of incoming email to happen during the SMTP connection stage, with a 5xx error code, while the sending server is still connected. In this case then the
386:
exploits the fact that the messages are sent in bulk, that is that they will be identical with small variations. Checksum-based filters strip out everything that might vary between messages, reduce what remains to a
1074:. By limiting the rate that email can be sent around what is typical for the computer in question, legitimate email can still be sent, but large spam runs can be slowed down until manual investigation can be done.
194:
these should be treated as dangerous. In any case, sender addresses are often forged in spam messages, so that responding to spam may result in failed deliveries – or may reach completely innocent third parties.
1096:'s feedback loop, and Network Abuse Clearinghouse, the domain's abuse@ mailbox, etc., ISPs can often learn of problems before they seriously damage the ISP's reputation and have their mail servers blacklisted.
203:
email client, risk entering a faulty reply address, and are typically not notified about delivery problems. Further, contact forms have the drawback that they require a website with the appropriate technology.
181:", might be written as "no-one at example dot com", for instance. A related technique is to display all or part of the email address as an image, or as jumbled text with the order of characters restored using
931:
on new accounts to verify that it is a real human registering the account, and not an automated spamming system. They can also verify that credit cards are not stolen before accepting new customers, check
232:
Avoiding or disabling this feature does not help avoid spam. It may, however, be useful to avoid some problems if a user opens a spam message: offensive images, obfuscated hyperlinks, being tracked by
1003:
back to the supposed sender. However, if (as is often the case with spam), the sender information on the incoming email was forged to be that of an unrelated third party then this bounce message is
771:
Spamtrapping is the seeding of an email address so that spammers can find it, but normal users can not. If the email address is used then the sender must be a spammer and they are black listed.
704:
fields in the header in order to hide their identity, or to try to make the email look more legitimate than it is, many of these spoofing methods can be detected, and any violation of, e.g.,
1050:
can be used to intercept all port 25 (SMTP) traffic and direct it to a mail server that enforces rate limiting and egress spam filtering. This is commonly done in hotels, but it can cause
255:
An email user may sometimes need to give an address to a site without complete assurance that the site owner will not use it for sending spam. One way to mitigate the risk is to provide a
1147:
can have a significant impact on spamming activity. Where legislation provides specific text that bulk emailers must include, this also makes "legitimate" bulk email easier to identify.
471:
Many spammers use poorly written software or are unable to comply with the standards because they do not have legitimate control of the computer they are using to send spam (
1816:
600:
is on spam recipients, sending networks also experience financial costs, such as wasted bandwidth, and the risk of having their IP addresses blocked by receiving networks.
1635:
131:
There are a number of techniques that individuals can use to restrict the availability of their email addresses, with the goal of reducing their chance of receiving spam.
757:
SMTP proxies allow combating spam in real time, combining sender's behavior controls, providing legitimate users immediate feedback, eliminating a need for quarantine.
700:
Header filtering looks at the header of the email which contains information about the origin, destination and content of the message. Although spammers will often
479:
will accept, a mail administrator can reduce spam significantly - but this also runs the risk of rejecting mail from older or poorly written or configured servers.
999:
If a receiving server initially fully accepts an email, and only later determines that the message is spam or to a non-existent recipient, it will generate a
1463:
899:
If a recipient periodically checks his spam folder, that will cost him time and if there is a lot of spam it is easy to overlook the few legitimate messages.
1591:
2008:
954:— to harass them, or to make the company or organisation appear to be spamming. To prevent this, all modern mailing list management programs (such as
277:" technique). Ham passwords are often combined with filtering systems which let through only those messages that have identified themselves as "ham".
178:
to prevent it from being automatically collected in this way, but still allow a human reader to reconstruct the original: an email address such as, "
1150:
Increasingly, anti-spam efforts have led to co-ordination between law enforcement, researchers, major consumer financial service companies and
2226:
1925:
1777:
1503:
1213:
Channel email is a new proposal for sending email that attempts to distribute anti-spam activities by forcing verification (probably using
53:
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they do accept a message, they will typically then analyze the content further – and may decide to "quarantine" any categorised as spam.
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1362:
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1605:
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1125:(TOS) agreement that discourages spammers from using their system and allows the spammer to be terminated quickly for violations.
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Some email mail transfer agents will perform FCrDNS verification on the domain name given in the SMTP HELO and EHLO commands. See
1627:
1376:
fully investigated. If we determine there is a problem with spam, we will take the appropriate action to resolve the situation.
791:
Statistical, or
Bayesian, filtering once set up requires no administrative maintenance per se: instead, users mark messages as
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legitimate email servers should retry the next higher numbered MX, and normal email will be delivered with only a brief delay.
2026:
1424:
1397:
576:, or store them for analysis by the entity operating the honeypot that may enable identification of the spammer for blocking.
300:
In many countries consumers may also report unwanted and deceptive commercial email to the authorities, e.g. in the US to the
1983:
1443:
738:, nearly all callbacks are to innocent third party mail servers that are unrelated to the spam; (2) When the spammer uses a
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are all now widely supported with growing adoption. While not directly attacking spam, these systems make it much harder to
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forwarded. Disposable email addresses can be used by users to track whether a site owner has disclosed an address, or had a
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639:
625:
466:
1977:
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2103:
1186:
904:
Measures that imposes costs on a third party server may be considered to be abuse and result in deliverability problems.
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1477:
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administrators enable them, leaving the receiving SMTP server no effective way to validate the sender's email address.
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1317:
31:
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1229:
1151:
171:
1564:
1140:
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2133:
2098:
1962:
1952:
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301:
250:
1460:
1993:
Historical
Development of Spam Fighting in Relation to Threat of Computer-Aware Criminals, and Public Safety
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341:
326:
1675:
2071:
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642:(FCrDNS) verification and if there is a valid domain name, put it into the "Received:" trace header field.
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When a mail server rejects legitimate messages, the sender needs to contact the recipient out of channel.
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From 2000 onwards, many countries enacted specific legislation to criminalize spamming, and appropriate
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1083:
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1968:
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1004:
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832:
716:, standards on how the header is to be formed can also serve as a basis for rejecting the message.
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1023:
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1992:
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1921:
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1709:
1681:
1654:
1354:
666:
597:
141:
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Refuse connections from hosts that give an invalid HELO – for example, a HELO that is not an
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line of an email message (or appended to the "username" part of the email address using the "
2372:
2319:
1996:
1913:
1888:
1169:
by a given piece of spam can often be followed up with domain registrars with good results.
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979:
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When legitimate messages are relegated to a spam folder, the sender is not notified of this.
824:
705:
507:
119:) – and the associated costs in time, effort, and cost of wrongfully obstructing good mail.
17:
2023:, and other countries' laws and pending legislation regarding unsolicited commercial email.
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812:
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2354:
2088:
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into the middle of each of their messages, to make each message have a unique checksum.
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2364:
2314:
2256:
2179:
2169:
2113:
2020:
1214:
1155:
1000:
735:
605:
353:
286:
175:
144:" so that each recipient does not get a list of the other recipients' email addresses.
112:
1793:
630:
The PTR DNS records in the reverse DNS can be used for a number of things, including:
542:– The email servers for any given domain are specified in a prioritized list, via the
64:
2411:
2329:
2294:
2194:
2128:
2016:
1811:
1193:
1166:
1051:
500:
all legitimate messages from first-time senders will experience a delay in delivery.
274:
261:
2032:
1421:
799:
and the filtering software learns from these judgements. Thus, it is matched to the
2377:
2334:
2304:
2154:
1440:
1389:
951:
945:
840:
734:
Callback verification has various drawbacks: (1) Since nearly all spam has forged
584:
30:"Spam blacklist" redirects here. For Knowledge (XXG)'s spam control mechanism, see
1944:
AOL's postmaster page describing the Anti-Spam
Technical Alliance (ASTA) Proposal
1917:
1196:
attempts to make spamming less profitable by bringing lawsuits against spammers.
2339:
2149:
1525:
1030:
traffic (TCP port 25) from machines on the network that are not supposed to run
955:
775:
713:
709:
511:
398:
222:
179:
1217:
so back-scatter does not occur) when the first email is sent for new contacts.
2309:
2286:
2159:
2118:
2080:
1980:– what to send, how to send it, where to send it – and what not to send or do.
1036:
836:
808:
752:
237:
216:
167:
101:
1649:
Leonard, Clifton; Svidergol, Brian; Wright, Byron; Meloski, Vladimir (2016).
880:
Measures to protect against spam can cause collateral damage. This includes:
2344:
2324:
2199:
1986:
E-Mail
Spamming countermeasures: Detection and prevention of E-Mail spamming
1504:"Australian government lags UK in deploying DMARC email spoofing prevention"
1144:
1059:
816:
692:
Content filtering techniques rely on the specification of lists of words or
662:
547:
543:
108:
475:). By setting tighter limits on the deviation from RFC standards that the
1314:
884:
The measures may consume resources, both in the server and on the network.
2389:
2299:
2184:
2164:
2063:
1902:"Spam Mail Detection Using Artificial Neural Network and Bayesian Filter"
1159:
959:
766:
670:
529:
Refusing to accept email whose HELO/EHLO argument does not resolve in DNS
388:
357:
1829:
1295:
1070:
Machines that suddenly start sending lots of email may well have become
1039:
via port 25 and to other smart hosts via the email submission port 587.
2271:
2189:
2123:
1529:
1114:
1089:
928:
866:
include the Labrea tarpit, Honeyd, SMTP tarpits, and IP-level tarpits.
828:
425:
There are large number of free and commercial DNS-based
Blacklists, or
293:
233:
159:
2002:
1410:
Canada's anti-spam legislation (CASL) is in place to protect
Canadians
526:
Refusing connections from hosts that give an obviously fraudulent HELO
107:
No technique is a complete solution to the spam problem, and each has
1854:
1561:
950:
A malicious person can easily attempt to subscribe another user to a
609:
163:
2009:
Mail DDoS Attacks through Mail Non Delivery Messages and Backscatter
1849:
1948:
1177:
Several approaches have been proposed to improve the email system.
396:
spammers will sometimes insert unique invisible gibberish known as
2349:
2108:
967:
915:
739:
573:
454:
443:
426:
420:
349:
334:
1906:
Intelligent Data Engineering and Automated Learning – IDEAL 2004
1706:
Introduction to Information Security: A Strategic-Based Approach
1606:"VRFY command—Verify whether a mailbox exists on the local host"
1249:"10 Tips to Avoid Spam | Digital Security Guide | Safeonline.ng"
1225:
Spam is the subject of several research conferences, including:
1027:
520:
496:
345:
330:
226:
2036:
807:
Software programs that implement statistical filtering include
731:
creating a bounce, but stopping just before any email is sent.
1908:. Lecture Notes in Computer Science. Vol. 3177. pp.
1677:
Virtual Honeypots: From Botnet Tracking to Intrusion Detection
1093:
182:
36:
1256:
1958:
2013:
1011:
server will report the problem to the real sender cleanly.
76:
1286:, Federal Trade Commission. URL accessed on 24 April 2006.
68:
1478:"DMARC Email Security Adoption Grows in U.S. Government"
1334:
Countering Spam by Using Ham Passwords (Email Passwords)
1277:
Email Address Harvesting: How Spammers Reap What You Sow
661:
authentication is strong enough that it can be used for
646:
72:
391:, and look that checksum up in a database such as the
60:
2005:, How to identify and protect yourself from spam email
1628:"On the dubious merits of email verification services"
1162:
activities and gathering evidence for criminal cases.
673:
cannot usually bypass this verification when they use
523:
or is an IP address not surrounded by square brackets.
1988:(Shawn Hernan, with James R. Cutler and David Harris)
1900:Özgür, Levent; Güngör, Tunga; Gürgen, Fikret (2004).
1984:
Computer Incident Advisory Committee's suggestions:
434:
or proxies; others list ISPs known to support spam.
356:, a common technique of spammers - but also used in
2363:
2285:
2212:
2142:
2079:
2070:
1973:
Coalition Against Unsolicited Bulk Email, Australia
1653:. Hoboken, NJ: John Wiley & Sons. p. 630.
1390:"Canada's Law on Spam and Other Electronic Threats"
174:. Address munging is the practice of disguising an
1881:Man quits job, makes living suing e-mail spammers
1850:"Results: 54,357 site shutdowns (67,095 pending)"
1731:Honeypots: A New Paradigm to Information Security
1315:Customers: TD Ameritrade failed to warn of breach
1807:"Two companies fined for breaching the Spam Act"
1466:2017-06-26 at Wikiwix. Tech Crunch. Jan 30, 2012
1351:This depends on provider's policy; for example:
111:between incorrectly rejecting legitimate email (
1088:By monitoring spam reports from places such as
304:(FTC), or similar agencies in other countries.
1387:The latter depends on local law; for example:
1054:problems, as well making it impossible to use
115:) as opposed to not rejecting all spam email (
2048:
411:address rather than any trait of the sender.
308:Automated techniques for email administrators
8:
2029:An article about spam in Scientific American
1755:"Shutting Down the Highway to Internet Hell"
1704:Shimeall, Timothy; Spring, Jonathan (2013).
1674:Provos, Niels; Holz, Thorsten (2007-07-16).
1062:if the port 587 submission port isn't used.
936:ROKSO list, and do other background checks.
922:Background checks on new users and customers
2076:
2055:
2041:
2033:
1733:. Boca Raton, FL: CRC Press. p. 252.
1775:Why can't I send mail from my hotel room?
1651:Mastering Microsoft Exchange Server 2016
1562:"4.XXX.XXX Persistent Transient Failure"
495:technique is built on the fact that the
1476:Kerner, Sean Michael (2 January 2018).
1461:DMARC Promises A World Of Less Phishing
1240:
1154:in monitoring and tracking email spam,
54:instructions, advice, or how-to content
1729:Joshi, R. C.; Sardana, Anjali (2011).
1400:from the original on 10 September 2014
1355:"Universal Terms of Service Agreement"
1253:Digital Security Guide | Safeonline.ng
909:Automated techniques for email senders
360:, and other types of fraud via email.
225:functionality, such as the display of
221:Many modern mail programs incorporate
1708:. Waltham, MA: Syngress. p. 74.
1699:
1697:
774:As an example, if the email address "
7:
1819:from the original on March 16, 2012.
1543:from the original on 8 December 2015
647:#Strict enforcement of RFC standards
1450:, NZ Department of Internal Affairs
461:Strict enforcement of RFC standards
63:so that it is more encyclopedic or
2242:Distributed Checksum Clearinghouse
1969:CAUBE.AU – Fight Spam in Australia
1959:Anti spam info & resource page
1830:Alleged Spam King Soloway Arrested
1794:Rate Limiting as an Anti-Spam Tool
1173:New solutions and ongoing research
940:Confirmed opt-in for mailing lists
393:Distributed Checksum Clearinghouse
25:
2227:Challenge–response spam filtering
2064:Unsolicited digital communication
1879:Paul Elias, (December 26, 2010).
1502:Stilgherrian (18 December 2018).
1332:David A. Wheeler, (May 11, 2011)
1296:"Information Technology: Threats"
1135:Email spam legislation by country
370:Challenge-response spam filtering
1862:from the original on 17 May 2008
1638:from the original on 2015-09-08.
1594:from the original on 2007-01-06.
1365:from the original on 4 July 2014
41:
1026:can be programmed to not allow
1200:Machine-learning-based systems
32:Knowledge (XXG):Spam blacklist
1:
1949:Anti-Spam Research Group wiki
1524:Jose Marcio Martins Da Cruz;
1109:Strong AUP and TOS agreements
781:Statistical content filtering
640:forward-confirmed reverse DNS
626:Forward-confirmed reverse DNS
27:Methods to prevent email spam
1918:10.1007/978-3-540-28651-6_74
1582:"Frequently Asked Questions"
1255:. 2016-09-07. Archived from
1187:Cost-based anti-spam systems
1165:Analysis of the sites being
18:Anti-spam techniques (users)
1353:Go Daddy Legal Department.
1205:legitimate email contents.
1048:Network address translation
453:' Domain Block List (DBL),
302:US Federal Trade Commission
2439:
2262:Naive Bayes spam filtering
1184:
1152:Internet service providers
1132:
1081:
1078:Spam report feedback loops
992:
977:
943:
873:
850:
784:
764:
750:
723:
720:SMTP callback verification
685:
619:
608:or are participating in a
564:
464:
441:
418:
367:
364:Challenge/response systems
320:
284:
248:
245:Disposable email addresses
214:
158:Email addresses posted on
151:
104:(unsolicited bulk email).
29:
1117:providers have either an
839:, and later revisions of
172:e-mail address harvesting
2237:Disposable email address
2099:Directory harvest attack
1963:Federal Trade Commission
1535:Anti-Spam Research Group
591:Outbound spam protection
379:Checksum-based filtering
251:Disposable email address
189:Avoid responding to spam
2027:Secret to Stopping Spam
1978:Composing abuse reports
1951:, which was created by
1835:March 17, 2009, at the
1282:April 24, 2006, at the
989:Limit email backscatter
787:Bayesian spam filtering
444:DNSBL § URI DNSBLs
406:Country-based filtering
327:Sender Policy Framework
1887:on December 27, 2010.
1784:AskLeo!, December 2005
616:PTR/reverse DNS checks
1680:. Pearson Education.
1119:Acceptable Use Policy
1084:Feedback Loop (email)
974:Egress spam filtering
827:, the email programs
726:callback verification
686:Further information:
677:to forge the domains.
638:(mail servers) use a
620:Further information:
465:Further information:
384:Checksum-based filter
321:Further information:
236:, being targeted by
211:Disable HTML in email
2247:Email authentication
2003:Email Security Guide
1587:The Spamhaus Project
1221:Research conferences
1043:Port 25 interception
1032:Mail Transfer Agents
934:the Spamhaus Project
682:Rule-based filtering
636:mail transfer agents
567:Honeypot (computing)
415:DNS-based blacklists
323:Email authentication
229:, URLs, and images.
100:are used to prevent
98:anti-spam techniques
2094:Bulk email software
1757:. eWeek. 2005-04-08
1608:. IBM. 16 June 2017
1431:, OnGuardOnline.gov
995:Backscatter (email)
853:Tarpit (networking)
833:Mozilla Thunderbird
694:regular expressions
489:Temporary rejection
127:End-user techniques
61:rewrite the content
1955:and is still alive
1780:2006-01-10 at the
1567:2016-03-03 at the
1446:2016-02-24 at the
1427:2013-12-17 at the
1339:2012-02-04 at the
1320:2012-03-05 at the
1301:2016-03-07 at the
1181:Cost-based systems
1100:FROM field control
876:Scunthorpe problem
622:Reverse DNS lookup
534:Invalid pipelining
504:HELO/EHLO checking
467:SMTP RFC standards
170:are vulnerable to
2405:
2404:
2232:Context filtering
2208:
2207:
1927:978-3-540-22881-3
1815:. June 22, 2007.
870:Collateral damage
665:purposes because
94:
93:
16:(Redirected from
2430:
2373:Advance-fee scam
2320:Keyword stuffing
2077:
2057:
2050:
2043:
2034:
1997:Neil Schwartzman
1932:
1931:
1897:
1891:
1889:Associated Press
1883:, archived from
1877:
1871:
1870:
1868:
1867:
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1840:
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1803:
1797:
1796:eWeek, June 2004
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1264:
1245:
1209:Other techniques
1123:Terms of Service
1072:zombie computers
1015:Port 25 blocking
1005:backscatter spam
980:Egress filtering
736:return addresses
675:zombie computers
652:
580:Hybrid filtering
432:open mail relays
89:
86:
80:
45:
44:
37:
21:
2438:
2437:
2433:
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2431:
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2408:
2407:
2406:
2401:
2385:Make Money Fast
2359:
2355:URL redirection
2281:
2204:
2138:
2089:Address munging
2066:
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1940:
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1837:Wayback Machine
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1569:Wayback Machine
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1530:"URL filtering"
1523:
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1496:
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1470:
1459:Butcher, Mike.
1458:
1454:
1448:Wayback Machine
1439:
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1429:Wayback Machine
1420:
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1401:
1394:fightspam.gc.ca
1388:
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1341:Wayback Machine
1331:
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1322:Wayback Machine
1313:
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1303:Wayback Machine
1294:
1290:
1284:Wayback Machine
1275:
1271:
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1215:bounce messages
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728:
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688:Email filtering
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593:
582:
569:
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473:zombie computer
469:
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381:
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354:spoof addresses
337:
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275:plus addressing
270:
262:security breach
253:
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219:
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200:
191:
156:
154:Address munging
150:
148:Address munging
137:
129:
117:false negatives
113:false positives
90:
84:
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2365:Internet fraud
2361:
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2327:
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2317:
2315:Google bombing
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2297:
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2257:List poisoning
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2114:Email spoofing
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1938:External links
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1185:Main article:
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1156:identity theft
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1129:Legal measures
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1113:Most ISPs and
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1082:Main article:
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565:Main article:
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555:Quit detection
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483:Greeting delay
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442:Main article:
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419:Main article:
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368:Main article:
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317:Authentication
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287:Spam reporting
285:Main article:
282:
281:Reporting spam
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2129:Pink contract
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1259:on 2022-05-18
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1066:Rate limiting
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1052:email privacy
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50:This article
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39:
38:
33:
19:
2378:Lottery scam
2335:Scraper site
2305:Doorway page
2213:
2175:Mobile phone
2155:Cold calling
1985:
1972:
1905:
1895:
1885:the original
1875:
1864:. Retrieved
1853:
1844:
1839:May 31, 2007
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1759:. Retrieved
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1257:the original
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952:mailing list
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841:SpamAssassin
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761:Spamtrapping
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740:trap address
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663:whitelisting
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585:SpamAssassin
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59:Please help
51:
2340:Social spam
2252:Greylisting
2222:Client-side
2150:Auto dialer
1612:19 December
1526:John Levine
1509:20 December
1487:20 December
1441:"Anti-spam"
1404:5 September
1369:5 September
1359:GoDaddy.com
1145:enforcement
1141:legislation
1121:(AUP) or a
1037:smart hosts
956:GNU Mailman
653:HELO/EHLO .
634:Most email
493:greylisting
399:hashbusters
223:web browser
69:Wikiversity
2412:Categories
2345:Spam blogs
2310:Forum spam
2287:Spamdexing
2160:Flyposting
2119:Image spam
2081:Email spam
1961:of the US
1866:2008-05-23
1761:2008-05-31
1571:, IETF.org
1547:2 December
1263:2021-12-21
1236:References
1133:See also:
874:See also:
837:Mailwasher
809:Bogofilter
801:end user's
753:SMTP proxy
747:SMTP proxy
544:MX records
257:disposable
238:JavaScript
217:HTML email
168:chat rooms
142:bcc: field
135:Discretion
109:trade-offs
102:email spam
85:April 2024
77:Wikivoyage
2423:Anti-spam
2325:Link farm
2295:Blog spam
2214:Anti-spam
2180:Newsgroup
2170:Messaging
2072:Protocols
2014:Spam Laws
1060:SMTP-AUTH
1020:Firewalls
964:Majordomo
817:SpamBayes
561:Honeypots
548:nolisting
540:Nolisting
73:Wikibooks
52:contains
2418:Spamming
2390:Phishing
2300:Cloaking
2277:Spamhaus
2185:Robocall
2165:Junk fax
1860:Archived
1833:Archived
1817:Archived
1778:Archived
1636:Archived
1592:Archived
1565:Archived
1541:Archived
1464:Archived
1444:Archived
1425:Archived
1398:Archived
1363:Archived
1337:Archived
1318:Archived
1299:Archived
1280:Archived
1160:phishing
1056:STARTTLS
960:LISTSERV
929:CAPTCHAs
767:Spamtrap
671:phishers
667:spammers
451:Spamhaus
389:checksum
358:phishing
234:web bugs
160:webpages
96:Various
2272:SpamCop
2190:Spambot
2134:Spambot
2124:Joe job
1910:505–510
1115:webmail
1090:spamcop
1024:routers
1009:sending
847:Tarpits
829:Mozilla
797:nonspam
294:SpamCop
1971:, The
1924:
1855:KnujOn
1737:
1712:
1684:
1657:
1482:e-Week
1422:"Spam"
966:, and
916:DNSBLs
859:tarpit
825:CRM114
708:
657:names.
651:
610:botnet
574:DNSBLs
546:. The
510:
491:– The
427:DNSBLs
333:, and
164:Usenet
67:it to
2395:Voice
2350:Sping
2267:SORBS
2143:Other
2109:DNSWL
2104:DNSBL
1965:(FTC)
968:qmail
813:DSPAM
702:spoof
606:virus
455:SURBL
421:DNSBL
350:DMARC
335:DMARC
75:, or
2200:VoIP
1953:ASRG
1922:ISBN
1735:ISBN
1710:ISBN
1682:ISBN
1655:ISBN
1614:2018
1549:2015
1537:wiki
1511:2018
1489:2018
1406:2014
1371:2014
1230:TREC
1158:and
1143:and
1058:and
1028:SMTP
1022:and
831:and
821:ASSP
793:spam
714:7208
710:5322
669:and
624:and
598:spam
521:FQDN
512:5321
497:SMTP
348:and
346:DKIM
331:DKIM
227:HTML
65:move
1995:by
1914:doi
1094:AOL
795:or
706:RFC
508:RFC
477:MTA
342:SPF
183:CSS
166:or
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