Full Disclosure mailing list archives
Re: Idle scan rediscovered!!!
From: Tim <tim-security () sentinelchicken org>
Date: Fri, 5 May 2006 16:11:11 -0400
2. There seem to be something with ACK packets to exploit for idle-scanning: hping3 -A -r host -p 80 Gives back exploitable incremental IPID on a Linux 2.6.15 box.
Are you sure? Just because the sequences are predictable or even incremental for your source host doesn't mean it is exploitable. This is old information, but I would assume it is still the case (until someone presents hard evidence otherwise): "One good approach is to use connection or peer-specific IPID sequences. Solaris does this, and it severely limits the information attackers can glean about other connections. Linux 2.4 also uses peer-specific IPID values (see net/ipv4/inetpeer.c). In addition, Linux 2.4 zeros the IPID fields in packets with the DF (Don't Fragment) bit set. After all, IP defragmentation is the only critical use of the ID field. Another approach (used by OpenBSD) is to randomize the IPID sequence. This is difficult to get right -- be sure the sequence does not repeat and that individual numbers will not be used twice in a short period." This quote is taken from: http://www.insecure.org/nmap/idlescan.html So, if a host maintains a predictable sequence, but it maintains independent sequences for each destination it sends packets to, then it isn't exploitable. I haven't tested it in recent Linux kernels myself, but I also haven't seen anyone present solid evidence to the contrary of this older information. thanks, tim _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- Idle scan rediscovered!!! Joel Jose (May 05)
- Re: Idle scan rediscovered!!! Tim (May 05)
- Re: Idle scan rediscovered!!! Cedric Blancher (May 05)
- Re: Idle scan rediscovered!!! Cedric Blancher (May 05)
- Re: Idle scan rediscovered!!! Tim (May 05)
- Re: Idle scan rediscovered!!! Cedric Blancher (May 05)
- Re: Idle scan rediscovered!!! rembrandt (May 05)
- Re: Idle scan rediscovered!!! Tim (May 05)
- Re: Idle scan rediscovered!!! Tim (May 05)
- Re: Idle scan rediscovered!!! Cedric Blancher (May 05)
- Re: Idle scan rediscovered!!! Tim (May 05)