Intrusion detection with AIDE
If an intruder penetrates your system, it will not be long before they upload and replace key system files. This is done to hide malicious programs and cover up the intrusion. For example, the ls program may be replaced with a trojaned version, which hides files that have been uploaded to your system. The ps program is also often replaced to hide the fact that malicious programs have been installed. Installing an intrusion detection system (IDS) can give you a heads up on whether or not filesystems have been modified.
By Paul Virijevich at Linux.com
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