The US Internal Revenue Service says that cybercriminals obtained
personal identification numbers (PIN) from the IRS.gov website and tried
to use them to file fraudulent tax returns. The attackers used a bot to
enter Social Security numbers (SSN) into the system and were successful
in more than 10,000 instances. The attackers tried more than 450,000
SSNs.
https://fcw.com/articles/2016/02/10/irs-pin-attack.aspx
