The Justice Department has joined a whistleblower lawsuit that alleges that Symantec, the California-based computer software giant, overcharged the federal government and some states by tens of millions of dollars.

The suit claims that Symantec misrepresented to the General Services Administration the discounts it was offering commercial customers for its products. Since the government’s price for those products was based on the discounts commercial firms received, the government was charged a higher price, the suit says.

“When doing business with the government, honesty and transparency are essential,” U.S. Attorney Ronald C. Machen Jr. said in a statement. “We are committed to ensuring that contractors who do business with the federal government provide honest services, prices and products.”

Symantec denied the allegations, saying it takes “compliance rules seriously and believe we followed all GSA Schedule and state contract program rules. We have fully cooperated with the government throughout its investigation, which Symantec was alerted to and first publicly disclosed in June 2012.

“We deny any wrongdoing and are confident the prices paid by the government for Symantec products and services were fair and reasonable.

The suit was initially filed by the whistleblower, Lori Morsell, in 2012. Morsell continues to work for the company. The Justice Department joined the suit last week.

The contract was in place between 2007 and 2012 and involved hundreds of millions of dollars in software sales.