Security links:
One of the best do-it-yourself, homegrown firewall sites! (click on Linux IPFW Firewall Design Tool when you get there..)
Is your system SAFE? - submit an email address and they will give you a huge list of possible exploits a hacker could use against you.
Visual Traceroute - this will track people who you think or know are trying to hack your system. You need their IP address first (use portsentry if you don't have one. It's free) and it shows you on a cool map of the world.
Nslookup - even under subnets - who's in that domain? - this is useful to check subnet ip addresses and who's in which domain you know of.
Portsentry - a program designed to detect and respond to port scans against a target host in real-time.
Stealth Port Scanner link - (I will delete this comment once I attempt to compile it on Redhat 6.0+, SuSe, and FreeBSD)
Logcheck - This is a program that goes through /var/log directory and checks for unusual activity.
Port Numbers - The most complete listing of ports I've found.
Nmap - one of the best port scanner utilities - now available with a Graphical Front End Interface!
FTP Site for a bunch of trojans that you install on an computer once you have root to "cover" your tracks. I believe lrk-4.1.tar.gz is the most current.
Check how secure your computer really is!
General Firewall info:
A Great firewall "forensics" faq
Snort - a lightweight network intrusion detection system, capable of performing real-time traffic analysis and packet logging on IP networks
Security programs:
Note: After downloading these files, you *might* need to rename them to ".tar.gz" (instead of whatever file extension you download them as) because for some reason I have gotten complaints they are downloading in weird file extensions. Also, you will need to hold down the shift key while clicking on the file to download, instead of just "viewing" the file.
Ip spoofing code, password crackers, etc.
Any .c file (malicious/source/etc) I have with a short description of what it does as well.
Here is a packet sniffing program that compiles under Redhat 6.x
Modified 10/20/2000 by Kyle Davis