Detecting Suspect Traffic
To illustrate the differences in the output of ipchains and iptables firewalls, we first compare log entries generated by an nmap XMAS scan.
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.
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.
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 firstname.lastname@example.org.
|diff -u: What's New in Kernel Development||Sep 04, 2015|
|Android Candy: Copay—the Next-Generation Bitcoin Wallet||Sep 03, 2015|
|The True Internet of Things||Sep 02, 2015|
|September 2015 Issue of Linux Journal: HOW-TOs||Sep 01, 2015|
|September 2015 Video Preview||Sep 01, 2015|
|Using tshark to Watch and Inspect Network Traffic||Aug 31, 2015|
- diff -u: What's New in Kernel Development
- Using tshark to Watch and Inspect Network Traffic
- Problems with Ubuntu's Software Center and How Canonical Plans to Fix Them
- The True Internet of Things
- Android Candy: Copay—the Next-Generation Bitcoin Wallet
- September 2015 Issue of Linux Journal: HOW-TOs
- Firefox Security Exploit Targets Linux Users and Web Developers
- Concerning Containers' Connections: on Docker Networking
- Where's That Pesky Hidden Word?
- A Project to Guarantee Better Security for Open-Source Projects