Timing and protocol defects: Difference between revisions
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|popular=Medium | |popular=Medium | ||
|effective=High | |effective=High | ||
| | |harm=Low | ||
|where=MTA | |where=MTA | ||
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SMTP requires that clients wait for a 2xx response to the HELO or EHLO command before proceeding. One ant-spam technique, known as a ''premature pipeline check'', detects extra data in the input buffer prior to the server sending the HELO/EHLO response. | SMTP requires that clients wait for a 2xx response to the HELO or EHLO command before proceeding. One ant-spam technique, known as a ''premature pipeline check'' pr ''early talking', detects extra data in the input buffer prior to the server sending the HELO/EHLO response, or prior to any command if the server hasn't offered the PIPELINEING extension. | ||
Other protocol defects include: | |||
*Sending MAIL FROM without first sending HELO or EHLO | |||
*Omitting the angle brackets required in MAIL FROM and RCPT TO | |||
*Adding a space after the colon in MAIL FROM or RCPT TO | |||
*Syntactically invalid HELO/EHLO name | |||
If such data is found, the client has failed the test. The server might then reject the message, close the connection, blacklist the client, etc. | |||
Latest revision as of 08:08, 15 March 2008
| Anti-spam technique: Timing and protocol defects | |
|---|---|
| Date of first use: | |
| Effectiveness: | High |
| Popularity: | Medium |
| Difficulty of implementation: | Low |
| Where implemented: | MTA |
| Harm: | Low |
SMTP requires that clients wait for a 2xx response to the HELO or EHLO command before proceeding. One ant-spam technique, known as a premature pipeline check pr early talking', detects extra data in the input buffer prior to the server sending the HELO/EHLO response, or prior to any command if the server hasn't offered the PIPELINEING extension.
Other protocol defects include:
- Sending MAIL FROM without first sending HELO or EHLO
- Omitting the angle brackets required in MAIL FROM and RCPT TO
- Adding a space after the colon in MAIL FROM or RCPT TO
- Syntactically invalid HELO/EHLO name
If such data is found, the client has failed the test. The server might then reject the message, close the connection, blacklist the client, etc.
