[3][1][4] Since its January 13, 2005,[2] Microsoft releases the updated tool every second Tuesday of every month (commonly called "Patch Tuesday") through Windows Update, at which point it runs once automatically in the background and reports if malicious software is found.

Starting with version 5.1, released on June 11, 2013, support for Windows 2000 was dropped altogether.

The report also stated that, on average, the tool removes malicious software from 1 in every 311 computers on which it runs.

[6] In August 2013, the Malicious Software Removal Tool deleted old, vulnerable versions of the Tor client to end the spread of the Sefnit botnet (which mined for bitcoins without the host owner's approval and later engaged in click fraud).

Approximately two million hosts had been cleaned by October;[7][8][9] although this was slightly less than half of the estimated infections, the rest of the suspected machines presumably did not have their automatic Windows Updates enabled or manually run.