US financial institution Citigroup on Thursday admitted that hundreds of thousands of its credit card customers in North America became vulnerable to personal data thefts as its network suffered a cyber attack.

Citigroup said hacker/s breached the bank’s network and got access to customer’s names, account numbers and email addresses and other contact information. The group didn’t mention the specific number of affected customers, but a report published by the Financial Times states that the breach potentially affected as many as 200,000 customers.

Acknowledging the breach, Citigroup said in a statement, “During routine monitoring, we recently discovered unauthorized access to Citi’s Account Online in North America.”

Citigroup is the latest victim in series of hacking attack that have troubled many big companies over the past few months.

Sony was forced to shutdown its PlayStation Network services for more than a month after it discovered a sophisticated hack on its online entertainment system. Recently, hacker group attacked the website of Sony Pictures, SonyPictures. com, and stole personal data of more than 1,000,000 users.

Hackers also breached the security of US non-profit Public Broadcasting Service (PBS) and posted various fake stories, including the one that stated that dead rapper Tupac Shakur was found alive in New Zealand. Again, hackers targeted a private-sector FBI affiliate, called InfraGard, and stole emails, passwords and contact information belonging to about 180 users.