OSSEC / HIDS Rule 552

OSSEC / HIDS rule catalog

• Rule family: OSSEC / HIDS
• Rule ID: 552
• Definition status: Present in current source
• Alert message / subject: Integrity checksum changed again (3rd time).
• Rule level: 1
• Definition checked: 2026-10-21
• Alert behavior: Internal grouping or suppressed event; dependent rules may still alert.

Interpretation and response

This event is recorded as “Integrity checksum changed again (3rd time).” 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.

Rule ID

552

Status

The wiki marked this rule Active at the source revision. Current definition status is shown above.

Description

This rule detects when a monitored file changes. This may be an authorized change, or an unauthorized change and these changes should be investigated further.

Guidance

Some files that ASL uses are also monitored for changes to ensure that they are not changed by unauthorized users or via a malicious action. For example, if you change your systems whitelist or blacklist, you should expect ASL to report changes to these files:

/etc/asl/whitelist

/etc/asl/blacklist

However, if you did not change any of ASLs settings, for example your whitelists or blacklists, this may be an indication that a malicious use has changed these on your system. All of ASL’s configuration files are stored in /etc/asl. Changes to other directories are not related to the ASL GUI, and may have been conducted via other software, users, or even unauthorized or malicious users. You should always investigate file changes to verify that they were only conducted by authorized parties.

False Positives

A legitimate event may still trigger this rule. Review the surrounding activity before deciding whether it is malicious. This rule detects when files change, therefore, it is not recommended that you disable this rule. Instead, if you do not wish to be alerted when a specific file or files in a particular directory change, please log into the ASL GUI, click on the ASL tab, select the File Integrity menu options and modify your configuration to ignore this file or directory.

If you believe that this is a false positive, please report this to our security team can determine if this is a legitimate case, or if its clever attack on your system. Instructions to report false positives are detailed on the Reporting False Positives documentation page.

Tuning Recommendations

If you do not wish to monitor the file or directory reported as changed, log into the ASL GUI, click on the ASL tab, select the File Integrity menu options and modify your configuration to ignore this file or directory.

Source and revision

Migrated from HIDS_552, wiki page 412, revision 2816 (20121019). 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 .