When next week rolls around, a few people might not be very happy when they log onto their computers. And by few, I mean tens of thousands.

Why? The “DNS changer bot,” malicious software that has infected more than 570,000 computers around the world in the past year, is to blame.

The software was spread by international hackers running an online advertising scam. The FBI took down the hackers months back, but realized that turning off the malicious servers would result in no Internet for all the victims.

The solution — using two temporary, clean Internet servers to take over the infected one — worked, but was only short-term. Come 12:01 a.m. on Monday, July 9, it will be shut down, and victims that haven’t yet corrected the condition will no longer have Internet access.

Barely over half the infected users have removed the malicious software, but more than 277,000 users worldwide still have infected computers and don’t realize it. Almost a quarter of those are thought to be in the U.S., including 50 Fortune 500 companies, according to the Associated Press.

Checking whether your computer is infected, though, is easy: you just need to run a simple test.

Facebook (NASDAQ:FB) and Google (NASDAQ:GOOG) have been attempting to warn people about the issue, while Comcast (NASDAQ:CMCSA) has reached out to customers whose computers appeared to be affected.

Be sure to check your computer for the malicious software, or else your upcoming Monday morning might be even more manic than usual.

-Alyssa Oursler, InvestorPlace Editorial Assistant