The IRS says criminals used taxpayer-specific data from “non-IRS sources” to gain unauthorized access to 100,000 tax accounts. Security pundits say the breach offers ample evidence of authentication weaknesses prevalent today and also shows how interconnected unrelated data breaches can really be. The way this breach went down illustrates how large scale breaches have transformed personal information into public information or at least information publicly available on the black market. The authentication problems are two-fold. One is that agencies like the IRS don’t do enough to properly verify identity during enrollment for new accounts.”]
Source: https://www.darkreading.com/cloud/irs-attack-demonstrates-how-breaches-beget-more-breaches