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Recently installed OSSEC on Linux machine to test.

Most results are expected, however yesterday I received emails with a number of notifications about Integrity checksum changing on files such as /usr/bin/whoami /usr/bin/md5sum /usr/bin/ls and about another 50 similar files

Since I didn't install any new versions of these files, how do I find out what caused the integrity checksum to change 2 days after I installed the OSSEC program?


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up vote 6 down vote accepted

Two reasons are:

  • You've actually been hacked
  • Prelinking is enabled

You can disable prelinking by editing /etc/sysconfig/prelink from:




And running:

prelink -ua


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Thank you very much. That has explained the constant changes I saw. I then did some further searching and also found information on another option as well Source: – Eureka Ikara Nov 19 '10 at 4:18

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