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OSSEC / HIDS Rule 9953
- Rule family: OSSEC / HIDS
- Rule ID: 9953
- Definition status: Present in current source
- Alert message / subject: vpopmail: brute force (empty password).
- Rule level: 10
- Definition checked: 2026-10-21
- Configured frequency: 8
- Timeframe (seconds): 240
Correlation values are configuration attributes; event-count behavior depends on the manager version and parent rules.
Interpretation and response
This event is recorded as “vpopmail: brute force (empty password).” Review the originating log and the affected host or service to determine whether the activity was expected.
An OSSEC/HIDS event records or correlates activity. Blocking depends on the originating application and any separately configured Active Response policy; an alert alone does not prove that an attack was blocked.
Documentation
The following guidance was migrated from the historical wiki and reviewed against the rule definition. Legacy ASL product names and interface instructions refer to the versions documented then. Use the current metadata above and your installed configuration when interpreting thresholds, notification settings and response behavior.
Description
ASL has detected multiple failed attempts to access a vpopmail user account. This generally indicates that an attacker is trying to brute force mail accounts on this system or trying to find accounts on the system to spam or send malware. This rule specifically looks for 8 failed attempts in 240 seconds.
Troubleshooting
Solutions
We do not recommend you disable this rule. You could whitelist the IP, but the best solution is to fix the invalid username and/or 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 brute force mail accounts or to find email addresses to spam.
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 and/or password so its valid.
Please do not report this as a false positive unless ASL is incorrectly reporting an event that is not a login failure for your mail server. To report a false positive, please follow this process:
Additional Information
Similar Rules
External Articles
None.
Source and revision
Migrated from HIDS_9953, wiki page 555, revision 5115 (20140924). Documentation review: 2026-10-21. An archived wiki status of Active is not a current deployment status.
For assistance, provide the rule ID, installed product and rule version, and a sanitized event to Atomicorp support .