The contract award, posted on a government website on 30 September, describes it as a "sole source order", which means that no other company is considered capable of providing these services.
Equifax disclosed the breach of the date of up to 143 million Americans on 7 September. Later it said an additional 2.5 million people could be affected.
The IRS has suffered its own embarrassing breaches, with the agency announcing on 6 April that the personal data of up to 100,000 US taxpayers could have been compromised.
Equifax initially said it had discovered the breach in July but it later turned out that the discovery had actually taken place in March.
It blamed a vulnerability in the Java Struts Web application framework for the breach.
According to a report issued about the breach by private security contractor Mandiant, two systems that support Equifax’s online dispute Web application were compromised by the attackers who also set up the means to remotely run commands on Equifax’s systems even if the vulnerability that had let them in was patched.
Remote access was made from about 35 “distinct public IP addresses”.
Mandiant said it had been unable to attribute the breach to any known hacking group that it tracks. It also said that the methods and tools used by the attackers did not match those of others of which it was aware.