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OSSEC / HIDS Rule 18161
- Rule family: OSSEC / HIDS
- Rule ID: 18161
- Definition status: Present in current source
- Alert message / subject: Windows Filtering Platform has blocked a connection
- Rule level: 2
- Definition checked: 2026-10-21
Interpretation and response
This event is recorded as “Windows Filtering Platform has blocked a connection”. 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
18161
Status
The wiki marked this rule Active at the source revision. Current definition status is shown above.
Description
This rule detects that the Windows Filtering Platform blocked a packet. This event logs all the particulars about a blocked packet, including the filter that caused the block.
Application Information:
Process ID: process ID specified when the executable started as logged in 4688 Application Name: the program executable on this computer’s side of the packet transmission
Examples of this alert from the Windows Endpoint
Examples of 5152 The Windows Filtering Platform blocked a packet.
Application Information:
Process ID: 1132Application Name: \device\harddiskvolume1\windows\system32 \svchost.exe
Network Information:
Direction: InboundSource Address: 192.0.2.10Source Port: 5355Destination Address: 192.0.2.11Destination Port: 56253Protocol: 17
Filter Information:
Filter Run-Time ID: 0Layer Name: Receive/AcceptLayer Run-Time ID: 44
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.
Similar Rules
Rule 18162: Windows Filtering Platform has blocked a connection multiple times (Standard: 3/10)
Outside References
Source and revision
Migrated from HIDS_18161, wiki page 698, revision 6005 (20190603). 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 .