According to the story, an eagle-eyed Unix engineer, only identified as SK, found the script "by accident." Kudos for being observant.
[The logic bomb] was allegedly placed by Rajendrasinh Makwana, an IT contractor who worked in Fannie Mae's Urbana, Md., facility. It was set to execute on Jan. 31. Had it done so, Fannie Mae engineers expect it would have caused millions of dollars in damage and possibly shut down the government-sponsored mortgage lender for a week.
Makwana was indicted for unauthorized computer access Tuesday in federal Court.
But the story shows the importance of de-provisioning users, quickly:
The discovery occurred on Oct. 29. Makwana had been terminated as a Fannie Mae contractor on Oct. 24, around 1 or 1:30 p.m., the affidavit says, but his network access was not terminated until late that evening. Makwana was fired for allegedly creating a computer script earlier that month that changed server settings without the permission of his supervisor.
Makwana was not required to turn in his badge or Fannie Mae-supplied laptop until the end of the day on Oct. 24. According to Nye's affidavit, it was during that afternoon that Makwana is alleged to have planted the malicious script.
There are two layers of defenses, that I can think of, offhand, that can be proactively taken to protect your organization from such an event. First: thorough background checks. While this won't screen everyone who could potentially be a bad character, it will screen those who have no business having admin privileges to critical IT systems.
The second layer of defense is having an identity and access control management system in place so that terminated employees -- especially those with network admin privileges -- can have their network access shut down immediately.
There is no reason why network access should have been possible after the talk with HR. None.
Perhaps Makwana is innocent, and someone else planted the logic bomb. That will be argued out in court. I'm certain that when network access is cut, a terminated admin can't plant logic bombs.
Fannie Mae is fortunate that SK was sharp enough to spot this script before it was set to trigger.