On Tuesday, U.S. citizens learned about the widespread 'Heartbleed bug' that invades websites and steals personal security information. By Friday, however, they learned that the U.S. National Security Agency knew about the security flaw for at least two years now.

The NSA, an agency that carries a mission to "protect U.S. national security systems" is also accused of regularly using the hacking bug to gather critical intelligence, two people familiar with the issue told Bloomberg News.

The agency's choice to keep the bug secret while actively pursuing national security interests, brings into further question the role the government's top computer experts play in American society.

'Heartbleed' was dubbed one of the biggest glitches in the Internet's history, a flaw found present in at least two-thirds of the world's websites. The discovery, made by researchers who also came up with a solution, prompted Internet users to change their passwords. The flaw even affected governments. Canada quickly suspended its electronic tax filing system, and computer companies including Cisco Systems Inc. to Juniper Networks Inc., scrambled to fix the problem in their network.

Bloomberg News reports that by storing the Heartbleed bug in its arsenal, the NSA obtained passwords and other basic information to aid in their hacking operations. The bug left millions of everyday users susceptible to the hacking of other nations' intelligence arms and criminal hackers.

Click here for more information about the Heartbleed bug and how to test if your favorite sites are affected.