From The Hill:

Just before that Christmas Day attack, in early November 2009, I was ordered by my superiors at the Department of Homeland Security to delete or modify several hundred records of individuals tied to designated Islamist terror groups like Hamas from the important federal database, the Treasury Enforcement Communications System (TECS). These types of records are the basis for any ability to “connect dots.”  Every day, DHS Customs and Border Protection officers watch entering and exiting many individuals associated with known terrorist affiliations, then look for patterns. Enforcing a political scrubbing of records of Muslims greatly affected our ability to do that. Even worse, going forward, my colleagues and I were prohibited from entering pertinent information into the database.