Equifax division TALX has a product called The Work Number, where prospective employers can verify job applicants' work history and previous salaries (it's also used by mortgage lenders and others): you can create an account on this system in anyone's name, provided you have their date of birth and Social Security Number. The former is a matter of public record, the latter is often available thanks to the many breaches that have dumped millions of SSNs (the latest being Equifax's catastrophic breach of 145,000,000 Americans' data).
Many readers probably consider their current and former salaries to be very private information, but as we can see this data is easily available on a broad spectrum of the working population in America today. The information needed to obtain it has been widely compromised in thousands of data breaches over the past few years, and the SSN and DOB on most Americans is for sale in a variety of places online. In short, if you can get these details from Equifax's online service, so can anyone else.Fortunately, you can reduce the likelihood that an acquaintance, co-worker, stalker or anyone else can do this by claiming your own account, changing the PIN and selecting a half-dozen security questions and answers. As always, it's best not to answer these questions truthfully, but to input answers that only you will know and that can't be found using social networking sites or other public data sources.
Equifax Breach Fallout: Your Salary History [Brian Krebs/Krebs on Security]