Archive for the ‘hacks’ Category

Defeating paranoid system administrators

Saturday, February 24th, 2007

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.

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Here comes the Sun

Sunday, March 5th, 2006

Yesterday I recovered two nice Sun Ultra 30 workstations (and one big Sun monitor) that were about to be thrown away at my office. They’re in quite good condition, apart from lots of dust and a cut keyboard cable. Apparently some smart guy thought that the quickest way to detach the keyboard was to cut the cable. In case you didn’t know, Sun keyboards have a small connector not unlike a standard PC keyboard or mouse, so just unplugging it certainly takes less effort than finding a cable cutter and applying the necessary force.

Of course I plan to install Debian GNU/Linux on at least one of them. In fact, I think I’ll put all the memory and both hard drives into one workstation and keep the other for parts.

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