How does LANguard System Integrity Monitor work? LANguard System Integrity Monitor will scan your system for important system files, and compute an MD 5 checksum for every important system file and store this in a database. At scheduled intervals, the LANguard S.I.M. will scan the list of monitored files, compute an MD 5 checksum again and test the current value against the stored value to determine if the file has been modified. If it detects a change, it will notify the system administrator via e-mail, and also log the occurrence in the security event log.