Flavio's blog » Unix http://flavio.stanchina.net challenging common wisdom since he was 3 Wed, 23 Feb 2011 23:18:11 +0000 en hourly 1 http://wordpress.org/?v=3.0.5 Defeating paranoid system administrators http://flavio.stanchina.net/2007/02/24/defeating-paranoid-system-administrators/ http://flavio.stanchina.net/2007/02/24/defeating-paranoid-system-administrators/#comments Sat, 24 Feb 2007 13:51:56 +0000 Flavio http://flavio.stanchina.net/?p=22 If a paranoid system administrator has blocked ssh access from Linux hosts to your office’s network — using the OpenBSD packet filter‘s fingerprinting — and you find yourself without access to the office’s mail server, you might want to make your Linux workstation’s TCP stack look like something else by changing the TTL, for example:

echo 128 > /proc/sys/net/ipv4/ip_default_ttl

The road to this hack is quite easy, anyway:

  1. install OpenBSD in a virtual machine;
  2. look hard at /etc/pf.os and look for possible useful differences;
  3. see that Linux uses a TTL of 64 while Windows XP uses 128;
  4. profit!

Item 1 was needed because I couldn’t find a copy of /etc/pf.os quickly, so I figured that it’d take less to just install an OpenBSD.

]]> http://flavio.stanchina.net/2007/02/24/defeating-paranoid-system-administrators/feed/ 0 setuid scripts? http://flavio.stanchina.net/2005/04/15/setuid-scripts/ http://flavio.stanchina.net/2005/04/15/setuid-scripts/#comments Thu, 14 Apr 2005 23:20:01 +0000 Flavio http://flavio.stanchina.net/?p=5 I knew setuid scripts are a security risk, but finally I found a thorough explanation.

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