After searching the duo's van, police found keys that opened the gas pump as well as address information for other stations in the area.

Mountain View officers set an alarm on the pump's circuit board hatch, which was triggered on Dec. 17. Officers arrested Tumasyan and Sarkisyan as they attempted to drive their van out of the Valero station at 334 San Antonio Road.

Police were initially tipped off on Dec. 6, 2010, when a gas station attendant discovered a small skimmer -- capable of harvesting credit card numbers from unwitting customers -- attached to the circuit board inside a gas pump, according to a press release issued March 8 by the Santa Clara County District Attorney's office.

Boris Tumasyan, 24, and Sarkis Sarkisyan, 23, -- both from Glendale, were charged with eight felony counts, including conspiracy, altering a computer and acquiring credit card information with intent to defraud, after Mountain View police successfully implemented a sting to catch the two men.

A pair of high-tech bandits were able to steal more than 3,600 credit card numbers with six electronic devices -- known as "skimmers" -- planted at five gas stations in Mountain View and Los Altos, according to the county district attorney.

The ease with which counterfeiters can produce and install the skimmers is exacerbated by the fact that many gas pumps can be opened with the same key, regardless of the brand, Flattery said.

A specialist in prosecuting high tech crimes, Flattery said it only takes "a matter of seconds" to install the skimming devices, which are made from modified commercial credit card scanners used by retailers. Skimmers record everything needed to produce an exact replica of a credit card.

In addition to the Valero, REACT officers found skimmers at three Shell stations in Mountain View -- 1288 W. El Camino Real, 110 N. Rengstorff Ave. and 807 N. Shoreline Blvd. -- along with one Chevron, located at 401 Main St. in Los Altos.

Flattery said he believes he has sufficient evidence, which includes video footage taken from the Mountain View Valero, to secure a conviction.

The two accused suspects are currently out on bail and scheduled to appear in court on April 14. They face a maximum of seven years, eight months in prison if they are convicted.

Consumers can feel safer if they go inside to pay the attendant or if they know that the stations they frequent have changed the locks on their pumps, he said.

He said this type of scheme is "especially frustrating to consumers," because it is impossible to know from the outside which pumps have been hacked. Law enforcement has to rely on the diligence of individual gas station owners.

Duo arrested in skimming scam

Men installed chips in local gas pumps to 'skim' customer info from credit cards