US Department of Homeland Security staff returning to work on Tuesday after the Presidents' Day holiday have apparently had a tough time getting computer systems to function.

DHS staff say they weren't able to log into computer systems at their offices in Washington DC, when clocking on this morning. Staff in at least four buildings, including US Citizenship and Immigration Services, are thought to be affected.

The problem occurred, at least one worker claims, with the personal identity verification cards used by employees as a form of two-factor identification, but it's not clear if this is the sole cause or just a symptom.

The timing of this outage is slightly concerning. A long weekend is the traditional time for IT to roll out new updates and fixes (and pick up some sweet overtime moolah), and these may have caused a problem.

However, long weekends are also a great time for hackers to make progress without being spotted. As we saw in the $81m Bangladesh bank hacking heist, the attackers picked their time so that the target and the banks needed to flag up money transfers were either away for the weekend or celebrating Chinese New Year.

It's a common enough tactic, and the DHS is a top target for foreign hackers. Luckily however, our computer systems are soon to be protected by President Trump's pick to head up cybersecurity, Rudy Giuliani. Judging from his website we'll be OK, after a long while and some updates.

The DHS had no comment at time of publication. ®