IPv6 Evasions, Scanners and the importance of staying current

Lots of activity on the IPv6 front lately. There was a talk on a conference on bypassing IDS using IPv6 tricks. Also a new scan tool (Topera) claimed to scan a host while staying below the radar of an IDS was released. To start with the latter, even though Suricata doesn’t have a dedicated port scan detector, the tool’s traffic lights up like a Christmas tree. The trick it pulls is to pack a lot of duplicate DST OPTS extension headers in the IPv6 packets. These options are just fillers, the only options they use are the “pad” option. In Suricata we’ve had an event for duplicate DST OPTS headers since 1.3 and the padding only headers generate an event in 1.4. Both alerts will be very noisy, so calling this a stealth attack rather dubious.

The other thing was a talk on IPv6 evasions, where the author compared Snort and Suricata. Suricata didn’t do very well. Sadly the authors chose not to contact us. On closer inspection it turned out an old Suricata version was used. Which one wasn’t specified, but as they did mention using Security Onion, I’m assuming 1.2. In the 1.3 branch (current stable) we’ve fixed and improved IPv6 in a lot of areas. Nonetheless, while testing the various protocol tricks, we did find some bugs that are now fixed in the git masters for the 1.3 stable branch and the 1.4 development branch.

I think these developments serve as a reminder that staying current with your IDS software’s version is critical. For that reason it’s too bad that distro’s like Security Onion, Debian, Ubuntu all lag significantly. The reasons differ through. For the guys from Security Onion it’s mostly a time problem (so go help them if you can!) for Debian and Ubuntu it’s actually policy. For that reason we’re providing PPAs for Ubuntu and for Debian we’re working on getting Suricata into the “backports” repo. The only mainstream distro that does it right for us is Fedora. They just update to the latest stable as soon as it’s out.

Given the complexity of protocols like IPv6 and the new developments all over the board, I see no viable case for staying on older versions. I know it’s a hassle, but stay current. It’s important.

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