Twelve financial firms have been fined a total of $14.4 million by the Financial Industry Regulatory Authority for failing to properly store client records, FINRA announced Thursday.

FINRA called the lax recordkeeping “significant deficiencies” in digital records that were supposed to be protected from alteration. The firms were supposed to keep records of broker-dealers and customers in a “write once, read many” format. “FINRA found that at various times, and in most cases for prolonged periods, the firms failed to maintain electronic records” in that format, the regulator says.

FINRA fined the following companies: Wells Fargo Securities LLC and Wells Fargo Prime Services LLC were jointly fined $4 million; RBC Capital Markets LLC and RBC Capital Markets Arbitrage S.A. were jointly fined $3.5 million; RBS Securities Inc. was fined $2 million; Wells Fargo Advisors LLC, Wells Fargo Advisors Financial Network LLC, and First Clearing LLC were jointly fined $1.5 million; Sun Trust Robinson Humphrey Inc. was fined $1.5 million; LPL Financial LLC was fined $750,000; Georgeson Securities Corporation was fined $650,000, and PNC Capital Markets LLC was fined $500,000.

The SEC has said the proper filing of records is “an essential part of the investor protection function because a firm's books and records are the primary means of monitoring compliance with applicable securities laws, including antifraud provisions and financial responsibility standards.”

Over the past decade, the volume of sensitive financial data stored electronically has risen exponentially and there have been increasingly aggressive attempts to hack into electronic data repositories, posing a threat to inadequately protected records, FINRA says. FINRA found that “each of these 12 firms had [recordkeeping] deficiencies that affected millions, and in some cases, hundreds of millions, of records pivotal to the firms’ brokerage businesses, spanning multiple systems and categories of records.”

The firms agreed to the fines without admitting or denying the charges.