The break-in comes just as the swelling ranks of the unemployed are turning to sites like Monster.com to look for work.

The company disclosed on its Web site that it recently learned its database had been illegally accessed. Monster.com user IDs and passwords were stolen, along with names, e-mail addresses, birth dates, gender, ethnicity, and in some cases, users' states of residence. The information does not include Social Security numbers, which Monster.com said it doesn't collect, or resumes.

Monster.com posted the about the breach on Friday morning and does not plan to send e-mails to users about the issue, said Nikki Richardson, a Monster.com spokeswoman. The SANS Internet Storm Center also posted a about the break-in on Friday.

USAJobs.com, the U.S. government Web site for federal jobs, is hosted by Monster.com and was also subject to the data theft. USAJobs.com also posted a about the breach.

Monster.com has been checking for misuse of the stolen information but hasn't yet found any, it said. It has made changes since discovering the break-in but won't discuss them because it doesn't discuss security procedures publicly and because it is still investigating the incident, Richardson said.