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SysAdmin: Linux Intrusion Detection

Dec 30, 2000, 23:00 (0 Talkback[s])
(Other stories by Joe 'Zonker' Brockmeier)

"No matter how security minded you are, no matter how many updates and patches you apply, there's always a chance that someone will crack one of your systems. It's an unpleasant reality, but it's a fact: no system is 100% secure unless it's turned off, but how useful is that? Although it's important to spend time on prevention, you must also have a backup plan in the event that security is compromised. If one of your systems is cracked, immediate detection and damage control are essential to prevent an intruder from gaining access to other systems and causing irreparable problems."

"One key to intrusion detection is understanding the most common security exploits. This knowledge will allow you to set up a checklist for periodic security checks of your system. If you're running a DNS server, BIND is a favorite target for attack. BIND has a number of security issues and should be disabled if not needed. If you need BIND, be sure to check at least monthly for updates and fixes. CGI scripts are another point of vulnerability. If CGI can be avoided, it is probably best to do so. Under no circumstances should an administrator leave sample CGI scripts on a production server or run a Web server as root. The list of CGI issues is too great to include here, but the SANS Top Ten List of security threats contains useful tips about CGI and other vulnerabilities. There's no standard for how often these security audits should be performed, but careful administrators continually check for signs of intrusion. A comprehensive check should be performed at least monthly, if not more frequently."

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