Lexmark employees have been told to be on alert after their personal information was compromised online.

In a letter to employees, Lexmark officials say files containing personal information from some current and former workers were accessed by two unknown parties, last month. Those files contained names, addresses and social security numbers.

Lexmark told employees that there's no evidence that the information has been misused, but is offering employees enrollment in a credit monitoring service and identity theft insurance for a year, as a precaution.