Detecting Suspect Traffic

Use psad with ipchains/iptables rulesets to find TCP and UDPadvanced port scans and other such network baddies.
ipchains vs. iptables Logs

To illustrate the differences in the output of ipchains and iptables firewalls, we first compare log entries generated by an nmap XMAS scan.

ipchains

The ipchains messages in Listing 2 were generated by an nmap XMAS scan of TCP ports 79 through 81. Recall that an XMAS scan sets the FIN, URG and PSH flags. First the nmap command and output is listed followed by the corresponding ipchains output. Note that ipchains makes no mention of which TCP flags were set.

Listing 2. nmap Command and Output with ipchains Output

iptables

Listing 3. iptables Messages from TCP Session with Web Server

Now we perform the same nmap scan (the nmap command line and output is identical to the above ipchains example, so it is not repeated) and display the corresponding iptables output (see Listing 3). This time we can plainly see the FIN, URG and PSH flags set in the packets used in the scan.

Resources

email: mbr@cipherdyne.com

Michael Rash works as a senior security engineer for an ASP in Annapolis, Maryland. He holds a Master's in Applied Mathematics from the University of Maryland and has been tinkering with Linux since 1998. He can be reached at mbr@cipherdyne.com.

______________________

White Paper
Linux Management with Red Hat Satellite: Measuring Business Impact and ROI

Linux has become a key foundation for supporting today's rapidly growing IT environments. Linux is being used to deploy business applications and databases, trading on its reputation as a low-cost operating environment. For many IT organizations, Linux is a mainstay for deploying Web servers and has evolved from handling basic file, print, and utility workloads to running mission-critical applications and databases, physically, virtually, and in the cloud. As Linux grows in importance in terms of value to the business, managing Linux environments to high standards of service quality — availability, security, and performance — becomes an essential requirement for business success.

Learn More

Sponsored by Red Hat

White Paper
Private PaaS for the Agile Enterprise

If you already use virtualized infrastructure, you are well on your way to leveraging the power of the cloud. Virtualization offers the promise of limitless resources, but how do you manage that scalability when your DevOps team doesn’t scale? In today’s hypercompetitive markets, fast results can make a difference between leading the pack vs. obsolescence. Organizations need more benefits from cloud computing than just raw resources. They need agility, flexibility, convenience, ROI, and control.

Stackato private Platform-as-a-Service technology from ActiveState extends your private cloud infrastructure by creating a private PaaS to provide on-demand availability, flexibility, control, and ultimately, faster time-to-market for your enterprise.

Learn More

Sponsored by ActiveState