The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Monday, March 26, 2007

Notes on what geeks find interesting

I've been using Linux for over twelve years now, and I'm still learning it.

Today, Wlofie and I spent a few hours doing Stupid Shell Tricks under Linux—stuff like naming files “ ‥ ” (that's space period period space or even “ . * & ! prang” (that's space period space asterisk space ampersand space explanation point space "prang") or even “-rf *”—names that give the Unix shell fits (or naive users fits trying to get rid of such files).

From there, we ventured into the territory that crackers use to hide their activities under Unix systems. One such trick is the following command:

GenericUnixPrompt> hacker_tool || rm -rf ./

Kill the running hacker_tool process and all the files are removed. A process listing will only show the hacker_tool running. A smart cracker will zap or munge the history file of the shell. So that's a pretty hard thing to detect.

Another trick a cracker will do to make things difficult is:

GenericUnixPrompt> hacker_tool &
[1] 4532
GenericUnixPrompt> /bin/rm hacker_tool

This starts the hacker_tool, then the executable is removed. The program still runs since the code is in memory, but there's no way to actually recover the executable.

Or so I thought.

Wlofie showed me this though (at least, under Linux):

GenericUnixRootPrompt# cd /proc/4532
GenericUnixRootPrompt# cp exe /tmp/recovered_executable_file
	# or alternatively
GenericUnixRootPrompt# dd if=exe of=/tmp/recovered_execuable_file

Ah, the things geeks find interesting.

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