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OSSEC / HIDS Rule 3911
- Rule family: OSSEC / HIDS
- Rule ID: 3911
- Definition status: Present in current source
- Alert message / subject: Multiple connection attempts to courier from same source.
- Rule level: 10
- Definition checked: 2026-10-21
- Configured frequency: 30
- Timeframe (seconds): 20
Correlation values are configuration attributes; event-count behavior depends on the manager version and parent rules.
Interpretation and response
This event is recorded as “Multiple connection attempts to courier from same source.” 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.
The current rule explicitly disables Active Response for this event.
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.
Rule ID
3911
Status
The wiki marked this rule Active at the source revision. Current definition status is shown above.
Description
This rule detects multiple login connections to the Courier IMAP and POP3 servers from the same IP. The intent of this rule is to detect a malicious party attempting a denial of service attack, or attempting to brute force guess passwords. (Please see the Similar Rules section at the bottom)
The default settings are to detect 30 login connections in 20 seconds.
Historical response guidance
= False Positives = This rule can be falsely triggered if multiple users are using the same IP address, such as behind a firewall and multiple users trigger more than 30 login connections in 20 seconds. This can happen either with a large number of users, or an email client that can generate multiple connections at the same time (as with the IMAPX protocol).
If you believe that this is a false positive, then disable this rule or whitelist the source IP.
Tuning Recommendations
None.
Similar Rules
Source and revision
Migrated from HIDS_3911, wiki page 206, revision 4742 (20140407). 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 .