Is the stock market ripe for a cyber-attack?

And what exactly is the action or reporting protocol if such an attack were to happen?

These are the issues that keep U.S. Senator Mark Warner (D-Va) up at night. And as he lay awake, Warner penned a letter voicing his concerns to the Chairman of the Securities and Exchange Commission, according to a report on Business Insider.

The letter, sent August 1, focused on Reg SCI, which requires certain trading venues to notify the SEC when there has been an intrusion.

Warner’s letter detailed how he wants there to be more transparency about which firms are subject to the rule, and for investment advisers and broker-dealers to factor in compliance to Reg SCI when deciding where to trade stocks.

“Reg SCI was intended to strengthen the technology infrastructure of the US securities markets by reducing the occurrence of systems issues, particularly following several high-profile outages that had the potential to cause considerable harm to investor confidence,” he said.

Under Reg SCI, certain trading venues “must notify the SEC when system problems do occur, including compliance issues, system disruptions and system intrusions.” The entities subject to the rule include all exchanges, clearinghouses, Securities Information Processors (SIPs), and those Alternative Trading Systems (ATS) that exceed certain thresholds.

Business Insider reported that in his letter, Warner wrote the SEC has not publicly disclosed which market centers have become subject to Reg SCI, and as a result “investors are unable to determine whether their orders are being routed to market centers which are being held to the requirement of having a strong, audited cybersecurity program.”

“This includes any broker-dealer operated ATS’s, single-dealer internalizers, and wholesalers which handle a significant percentage of retail investor order flow and a high percentage of overall US average daily volume,” Warner’s letter said. “If compromised, these market centers could destabilize markets by not having the protections in place that the SEC has outlined in Reg SCI to strengthen the integrity of our markets.”

Warner has also written Jay Clayton on the topic of market rebates. In a missive dated July 14^th, he called for the end of rebates or payment for order flow.

Warner sits on the Senate Committee on Banking, Housing and Urban Affairs, the Committee on Finance and the Select Committee on Intelligence.