“ls” not working on Ubuntu 10.04

Question

All of the sudden the handy command ls stopped working on my Ubuntu 10.04 server.

The only thing I did was add a new entry to the PATH environment variable and that was all.

Here is the result from echo $PATH:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/root/java/bin

Why this is happening?

Also, I navigated to the /usr/bin folder and the ls program was there but I wasn't able to run it from there either.

Edit: 'ps' is also not working. I also tried to remove the lines I edited on .bashrc and nothing changes

Plus stat /bin/ls gives me this:

Size: 39696         Blocks: 80         IO Block: 4096   regular file
Device: 802h/2050d  Inode: 13377592    Links: 1
Access: (0755/-rwxr-xr-x)  Uid: (  122/ UNKNOWN)   Gid: (  114/ UNKNOWN)
Access: 2011-08-11 06:25:04.000000000 +0200
Modify: 2010-09-21 20:32:55.000000000 +0200
Change: 2011-07-24 17:22:39.000000000 +0200

Answer 1

Judging by the file size and this link, you have a rootkit on your system. The most sensible course of action is to make a backup of any personal data and reinstall from scratch.