Article 3 of the internet society of china Anti-Spam Code issued by internet society of china clearly stipulates that emails with the following attributes are called spam:
Advertisements, electronic publications, various forms of promotional materials and other promotional emails that the recipient has not requested or agreed to receive in advance;
E-mail that the recipient can't refuse;
E-mail that hides the identity, address, title and other information of the sender; E-mail containing false information sources, senders, routes and other information.
By comparing the mails sent by standard clients such as OutlookExpress and Webmail, we can find ten important features of spam:
(1) does not have an X-Mailer letterhead, or a special X-Mailer letterhead is used.
We see that there is an X-mailer in the email header sent Out-Look: Microsoft out-look IMO, build 9.0.2416 (9.0.2910.0). Spam either doesn't exist or has a header, such as x-mailer: ehoosend? .
(2) pleasantries. More polite spam will have polite expressions, such as "Please delete it conveniently", "Sorry to bother you" and "Excuse me? Forgive? " .
(3) Forge the sender. The MailFrom in the MTP command is inconsistent with the From in the mail body, and the email address of the sender is not the real email address.
(4) Send through dynamic IP such as ADSL. External users directly connect to MX server through dynamic IP, but SMTP service is not provided locally, so IP cannot be interpreted reversely.
(5) Send tool signature. Some * * * mass sending tools will have their own signatures in every letter they send.
(6) Do not use the standard MIME format. The mail format is not standard, but OutlookExpress is compatible.
(7) The sending time exceeds the current time. In order to keep the first position of the client, some spam will forcibly change the sending time to an early time.
(8) forwarded by many servers. There are more than three recipients on the letterhead.
(9) The message content has a special HTMLtag. In order to embed more content and scripts, spam often uses some HTMLtag that are not used by normal mail. Such as iframe, frameset, object and so on.
(10) The contents of the letter have instructions to cancel the subscription or no longer accept such emails. This is often a bigger trap for the sender. Once you click on the corresponding link, you will receive more spam.
Extended data:
Anti-spam technology can be divided into four categories: filtering, reverse lookup, challenge and encryption. These solutions can reduce the spam problem, but they all have their limitations.
Spam has brought great influence to the Internet and users. This influence not only requires people to spend time dealing with spam and occupy system resources, but also brings many security problems.
Obviously, spam takes up a lot of network resources. Some mail servers are regarded as spam forwarding stations because of poor security, and events such as warnings and IP blocking occur from time to time. It consumes a lot of network resources, which slows down the normal business operation.
With the development of global anti-spam and the sharing of blacklists among institutions, innocent servers are blocked in a wider range, which will undoubtedly cause serious problems to normal users.
Spam is more and more closely combined with hacker attacks and viruses. For example, SoBig worm installed an open proxy that can be used to support mail forwarding. With the development of spam, the use of malicious code or monitoring software to support spam has increased significantly.
On June 5438+February 3, 20031,a hacker organization in Brazil sent spam containing malicious javascript scripts to millions of users. Those who browse spam through Hotmail inadvertently reveal their accounts.
Another example is the recent display problem of IE's website. Adding "%0 1" before the host name can hide the real host address, which can be found within a few weeks after the spam is published.
More and more deceptive virus mails have made many enterprises suffer greatly. Even if a good network protection strategy is adopted, it is still difficult to avoid. More and more security incidents are caused by emails, which may be viruses, Trojans or other malicious programs.
It is really difficult for ordinary users to make a correct judgment on fishing fraud tricks, but the losses caused are very direct.
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