[CentOS] Commands failing silently?

Dan Bongert dbongert at wisc.edu
Mon Mar 24 21:18:49 UTC 2008


Bill Campbell wrote:
> On Mon, Mar 24, 2008, Dan Bongert wrote:
>> Hello all:
>>
>> I have a couple CentOS 4 servers (all up-to-date) that are having strange 
>> command failures. I first noticed this with a perl script that uses lots of 
>> system calls.
>>
>> Basically, sometimes a command just won't run:
>>
>> thoth(52) /tmp> ls
>>
> ...
>> thoth(66) /tmp> uname -a
>> Linux thoth.ssc.wisc.edu 2.6.9-67.0.7.ELsmp #1 SMP Sat Mar 15 06:54:55 EDT 
>> 2008 i686 i686 i386 GNU/Linux
>>
>> Nothing in either dmesg or /var/log/messages seems to indicate any 
>> problems. It also doesn't seem to matter what the command is -- ls is the 
>> quickest test, but sshd will sometimes to fail to spawn children, etc. 
>> There aren't a large amount of processes on the machine either -- only 122 
>> at the moment.
> 
> There is a very good chance that the machine has been cracked,
> and the system's /bin/ls routine replaced by one hacked to hide
> the cracker's programs.  ``rpm -V coreutils procps util-linux''
> may well show several critical programs changed.

Everything seems OK there:


thoth(96) /tmp> sudo rpm -V coreutils procps util-linux

> You can also try running ``strace /bin/ls'' to see what is going on.

Funnily enough, running strace will work just fine. Though, as I said, just
about any command will fail -- 'ls' was just for testing purposes.

> Bill
> --
> INTERNET:   bill at celestial.com  Bill Campbell; Celestial Software LLC
> URL: http://www.celestial.com/  PO Box 820; 6641 E. Mercer Way
> FAX:            (206) 232-9186  Mercer Island, WA 98040-0820; (206) 236-1676
> 
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-- 
Dan Bongert                     dbongert at wisc.edu




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