DALLAS (CBS11) – For the second day, a computer virus has disrupted or slowed systems at the City of Dallas.

Users looking to access online library searches, or pay tickets online were greeted with a frustrating message: technical difficulties.

“There is not a safe that hasn’t been cracked,” says Keith Barthold, CEO of DKB Innovative with a wry laugh. Not exactly comforting words. But, the warning from the local cybersecurity expert is at least timely.

“There are a lot of bad guys out there trying to get data, disrupt and take down organizations,” says Barthold, often he says simply to “create chaos.”

A city spokesperson tells CBS 11 no personal data has been compromised and that responses to 911 calls weren’t delayed. However, the police Computer Aided Dispatch system was disrupted for a time on Monday as city staffers worked on a fix.

A spokesperson says the CAD system was back up and running by Monday evening. But, the problems for other departments continued into Tuesday. So what’s a city to do?

Barthold says large scale cybersecurity typically involves constant surveillance, and artificial intelligence to stop an attack if there is one and quickly seal it from further damage.

“Everyone’s vulnerable,” says Barthold.

It was just last year that police and the FBI launched an investigation after someone hacked Dallas’ citywide siren system. So should IT staffers have been better prepared?

“I don’t think it’s a fair criticism,” says Barthold. “You’ve got to understand the complexity of IT in a municipal environment as big as Dallas is.”

He does say that computer protection at home or at City Hall should include multiple layers.

“Just like a bank has security cameras, and guards at the door, and a vault, you’ve got to have multiple defenses,” advises Barthold. “That means good passwords, good discipline around usage of passwords and your browsing activities and educating yourself what’s fake versus what’s real: and being very careful of what you click on.”

So far, there’s been no word from city staffers on how the virus gained access to the city’s computer systems, nor how long the disruptions are expected to last.