(NBC News)  More Christmas shoppers are carrying mobile devices this year, which means they're more are likely to fall victim to cyber-crooks and thieves.

"The number one thing you can do, and it's a real simple thing to do, is add a password to your phone.  It will help protect the data that you have on there," advises Symantec's Kevin Haley.

Possibly a bigger risk is getting hacked because you're using the wrong WiFi.  

"It's always possible that somebody in a free WiFi setting could be listening in," Haley warns.

Verizon security expert Wade Baker says the safest thing to do is just shut off the WiFi and use your own plan for internet access.

Short of that, don't do anything very important while on public WiFi.

"If you are on a public network, make sure it's a legitimate one, make sure it is the one offered by Starbucks or the actual airport rather than some guy sitting in the corner," Baker warns.

And if you insist on buying online from your mobile device, only enter personal information when there's an "S", for secured" at the end of the "HTTP".