Some employers will outsource this task to third party organizations. In some cases employers or the firms they contract will conduct more extensive background checks which may also include an evaluation of your credit history and criminal record, depending on the type of job you are applying for.
Get the Facts Straight
Be sure that you provide accurate information on your job applications and resume. Don't guess as to where you worked when. If you don't remember the details recreate your work history before you apply. Here's how to find your employment history.
The bottom line is that candidates should be truthful with all information that they supply to prospective employers. You should proactively cultivate and supply positive recommendations to counter any potential negative feedback about your performance that might be uncovered as an employer checks on your employment background.
What Information Will Employers Share?
Former employers will generally not share information about your job performance. If employers contact staff at former employers through informal channels, this type of information might be divulged off the record.