Evidence of system hacks varies

How can you tell if your system has been compromised? Internet security firm Mandiant says there are numerous signs. Included are evidence of unauthorized use of valid accounts, trace evidence & partial files, command and control activity, known and unknown malware, suspicious network traffic, valid programs used for other purposes and files that have obviously been accessed by attackers. IT managers are reminded that threats can slip in undetected and lay dormant for long periods of time before striking.