A cyberattack on British broadband provider TalkTalk will be investigated by defense and security company BAE Systems, TalkTalk announced Sunday. Friday's cyberattack may have led to the theft of data belonging to more than 4 million customers, with TalkTalk saying it received a ransom demand from someone claiming responsibility for the attack.

"BAE Systems are supporting us as we investigate this week’s cyberattack," a TalkTalk spokeswoman said Sunday.

Cyberspecialists at BAE Systems are analyzing “vast quantities” of data to find out what information was stolen and how the attackers gained access to the TalkTalk system, said a spokeswoman for BAE Systems’ Applied Intelligence division.

In addition to BAE Systems’ examination, the Metropolitan Police Cyber Crime Unit is conducting a criminal investigation.

This most likely won't be the last cyberattack on TalkTalk, chief executive Dido Harding told the Guardian Sunday.

"Nobody is perfect," Harding said. "God knows, we’ve just demonstrated that our website security wasn’t perfect -- I’m not going to pretend it is -- but we take it incredibly seriously. ... On that specific vulnerability, it’s much better than it was and we are head and shoulders better than some of our competitors."

TalkTalk said Saturday the amount of information stolen in Friday's attack was "materially lower" than first feared although it was unable to say how many of its customers were affected.

This is the third major cyberattack on TalkTalk in the last 12 months.