|Alert Message||Multiple SASL authentication failures.|
Simple Authentication and Security Layer (SASL) is a framework for authentication and data security in Internet protocols, such as pop3, imap, postfix, courier, other smtp servers and even web services. Its most commonly used for mail services.
This alert means that a system or user has failed to authenticate to a service that uses SASL multiple times. This can be an indication that someone is trying to brute force attack an account, or it could mean a client has an incorrect password and/or username and keeps trying and failing to authenticate multiple times.
 Log example
Oct 8 10:33:03 host postfix/smtpd: warning: unknown[126.96.36.199]: SASL DIGEST-MD5 authentication failed: authentication failure
 False Positives
The rule itself can not generate a false positive, the rule just reports when multiple login failures happen from a single IP. If this event is not an attack, then this means the enduser has an invalid username and/or password configured for the service. The best solution to this problem is to have the user fix their username/password so its valid.
 Tuning Guidance
We do not recommend you disable this rule. You could whitelist the IP, but the best solution is to fix the invalid username/password for the user.
If you do not wish to shun on this rule, just change the Rules configuration for Active Response to "no". We do not recommend you disable active response on this rule, as this method is widely used to probe ssh servers.
 Additional Information
 Similar Rules
 Knowledge Base Articles
 Outside References