As head of the ever-expanding FBI computer intrusion squad, Trent Teyema has heard all the stereotypes about hackers, but he knows that people who call themselves that today are a long way from their counterparts of even a few years ago.

A hacker used to be a 12-year-old in the basement eating sweets and drinking cola, Teyema said. “That’s not the case anymore,” he added.

Teyema, who was speaking on Wednesday at a conference of the Computer Security Institute in Washington DC, said hackers today are often armed, operating in other countries, and capable of malicious acts far beyond identity theft and fraud.

As examples, he cited three cases in which the FBI has searched around the world to apprehend criminals who were far more dangerous than the stereotypical teenage geek.

In one case, a man cost phone companies hundreds of thousands of dollars by using phone bridges, opening and closing different phone lines, and taking advantage of shoddy infrastructure in communications procedures to make and receive calls around the world. When investigators finally caught up to him, he was armed and dangerous. After a short negotiation, the investigators arrested him.

Another case involved an extortion attempt by a man who had secured access to the computer network operating on the South Pole. Authorities ended up tracing the origin of the messages to an internet cafe in Romania, which Teyema said shows the importance of international co-operation among law enforcement officials.

“We’ve had great success [catching hackers] abroad,” he said. It is important to dispel the myth that suspects in US security breaches won’t be arrested if they are in foreign countries, Teyema added. “Other countries have become more sophisticated” in their ability to track down hackers, he said.

Antiterror legislation passed recently in Italy could reportedly curb the work of hackers as well, Teyema noted. The legislation is designed to enable increased government surveillance of internet activity.

He recalled an incident that revealed just how important stopping cybercrime can be. He told of a man who was sabotaging patent research companies by sending out explicit email messages to clients, purportedly from the company’s account. Authorities followed the man for months before being led to his apartment, where they were surprised to find illegal firecrackers, hand grenades and chemicals that Teyema said could be used to make weapons of mass destruction.

The sentence he was facing for the firecrackers alone was more than for the fraudulent email, Teyema said.