The feds are getting ready to come knocking. On Oct. 10, the Association of National Advertising sent a letter to its members sharing that the Federal Bureau of Investigation had contacted the ANA’s outside counsel Reed Smith LLP about assisting with its investigation into U.S. media buying practices. The Wall Street Journal first reported the investigation on Sept. 27. The ANA’s letter, signed by ANA CEO Bob Liodice, suggested next steps its members can take such as consulting with Reed Smith. Here’s what it’s all about:

What exactly is the FBI investigating?

It’s unclear. Steve Miller, a partner at Reed Smith who has had limited discussions with the FBI regarding the issue, said one aspect may be deception between media holding companies and advertisers.

“Hypothetically, Media Holding Company A owes an advertiser a rebate for the volume of purchases that they made and then through accounting dichotomy or deception or misleading conduct [the agency] tells them they didn’t earn the rebates,” Miller said.

So it’s just about rebates?

Probably not. An online advertising executive, with more than 20 years of experience, predicted the investigation will instead look into commercial fraud and tax evasion.

“Yeah there’s sports tickets, entertainment, taking someone’s family to the Bahamas, but those aren’t really big-ticket items. Then you start to see a couple companies a little more overtly suggesting and finding ways to put direct cash into the media agencies pockets,” the executive said.

Why now?

The executive said that while practices of bribery have been happening for decades, the practice has become more apparent through the globalization of media agencies and increased competition over the last 10 years.

“It wasn’t just getting P&G for Europe or Ford for Latin America. Agencies wanted to do full global deals. You could come into the U.S. market where you can’t make much margin, and it’s very competitive but you can make a lot of margin on rebates outside the U.S,” the exec said.

Miller said he assumes it was prompted by the ANA’s 2016 K2 Intelligence report titled “An Independent Study of Media Transparency in the U.S. Advertising Industry.” One media buyer saw political motivations, as in the Russian interference of 2016 election via Facebook and other platforms, as a reason for the timing of the investigation.

“In the past, it’s always been finger-pointing, musical chairs on the blame when fraud came up. My take: the real reason is an extension of the political landscape, and interference, extending to exploring this as laundering, funding nefarious acts,” said the buyer.

What kind of information is the FBI looking for?

Emails that reveal an intent to breach contracts. Miller imagined a scenario with two executives — Joe and Allen — in a media agency: Joe emails Allen, “We shouldn’t be doing this,” and Allen replies, “They’ll never find out.” Asked if that’s a common practice, the executive in online advertising emphatically said, “Yes.”

“In any white-collar investigation, the government will subpoena the internal records — emails within an organization, accounting records — to see internal discussion, if it’s inappropriate. They’re very thorough,” Miller said.

Who will be affected?

The ANA’s letter said the FBI investigation will begin with identifying advertisers who they believe may have been defrauded. ANA’s Liodice suggested members who think they’ve been defrauded to retain counsel as well as conduct their own audits.

“If it’s proven that advertisers have been defrauded then it’s likely to lead to major industry shakeups in terms of how they treat their customers as well as significant financial repayments, all contingent on finding wrongdoings,” Miller said.

What happens next?

This is going to take a lot of time. Digiday reached out to the five major holding companies, most of which didn’t respond to a request to comment. A WPP spokesperson emailed no comment. An Interpublic Group spokesperson also declined to comment but noted the agency’s 2016 statement addressing the ANA’s report: “Here at IPG we do not accept rebates in the U.S., nor do we believe rebates should be part of U.S. market practices,” the statement included.

An Omnicom spokesperson said the agency “has not been contacted by the FBI.”

Of course, that could change. The executive predicted that forthcoming interviews could result in people throwing each other under the bus.

“These people are worried about going to jail so they will tell the feds where to look when they go to the holding company records. Almost none of these people worked 25 years at one agency so when someone talks it’ll be a race to immunity: Who can name the most people, turn over the most emails, describe the most conversations to the feds so they can protect themselves,” the executive said.