WASHINGTON — Equifax Inc. took part of its website offline Thursday after code on the site redirected users to a malicious URL urging them to download malware.

Also Thursday, a top Republican congressman introduced a bill that would stop credit reporting companies such as Equifax from using Social Security numbers to verify Americans’ identities.

The moves come a month after Equifax revealed that a data breach exposed the Social Security numbers and birthdates of as many as 145.5 million Americans.

That hack took place after Equifax failed for several months to fix a software flaw that federal officials had warned about in March.

Late Wednesday night, independent security analyst Randy Abrams said in a blog post that while he was trying to download his credit report from the Equifax site, he clicked a link that kicked him to a third-party website with “one of the ubiquitous fake Flash Player Update screens.” His post was first reported by technology news site Ars Technica.

Equifax said Thursday that the problem stemmed from code provided by a third party.

“The issue involves a third-party vendor that Equifax uses to collect website performance data, and that vendor’s code running on an Equifax website was serving malicious content,” the company said in a statement. “Since we learned of the issue, the vendor’s code was removed from the webpage and we have taken the webpage offline to conduct further analysis.”

Equifax emphasized that its “systems were not compromised” and said that despite early reports, the problem “did not affect our consumer online dispute portal.”

Its spokespeople did not answer questions about when the company learned of the problem or how many website visitors clicked the link.

Separately, Rep. Patrick McHenry, R-N.C., introduced legislation Thursday that would crack down on credit reporting companies. It would require Equifax, Experian and TransUnion to phase out the use of Social Security numbers by 2020.

The legislation also would create a national framework for consumers to freeze access to their credit to prevent identity theft as well as mandating the federal government to create uniform cybersecurity standards for credit reporting companies and conduct onsite examinations.