How it works

  1. Wazuh agent scans the system and sends the checksums and attributes of the monitored files and Windows registry keys to the Wazuh manager. We can configure:

  • Frequency: By default, syscheck runs every 6 hours, but this is entirely configurable.

  • Real-time monitoring: Wazuh supports real-time file integrity monitoring on servers running Windows or Linux. Note that that the real-time option is only configurable for directories, not for single files.

  1. Wazuh manager stores the checksums/attributes and looks for modifications by comparing the new values to the old values. It's possible to configure syscheck to report a diff summary of the actual changes made to text files.

  2. An alert is generated if changes are detected on monitored files and/or registry keys.

It's possible to handle false positives using configuration options like ignore. You can also create rules that profile files that are to be excluded from FIM alerts.

Alert example, generated by syscheck:

** Alert 1460948255.25442: mail  - ossec,syscheck,pci_dss_11.5,
2016 Apr 17 19:57:35 (ubuntu)>syscheck
Rule: 550 (level 7) -> 'Integrity checksum changed.'
Integrity checksum changed for: '/test/hello'
Size changed from '12' to '17'
Old md5sum was: 'e59ff97941044f85df5297e1c302d260'
New md5sum is : '7947eba5d9cc58d440fb06912e302949'
Old sha1sum was: '648a6a6ffffdaa0badb23b8baf90b6168dd16b3a'
New sha1sum is : '379b74ac9b2d2b09ff6ad7fa876c79f914a755e1'