The White House remains vulnerable to new cybersecurity attacks, according to a memo obtained by Axios.

The internal memo, which warns that “the White House is posturing itself to be electronically compromised once again,” comes after at least a dozen high-level cybersecurity officials have resigned or been pushed out of office, Axios reports.

Dimitrios Vastakis, a senior White House cybersecurity director, wrote the Oct. 17 memo, which also served as his resignation letter. He previously worked in the Office of the Chief Information Security Officer (OCISO), which the Obama administration established in 2014 following a breach of an unclassified White House network by Russian hackers.

In July, the Trump administration dissolved the OCISO and gave its tasks to the Office of the Chief Information Officer.

Axios also reports that the Trump administration is trying to force out these senior-level cybersecurity staff — especially those hired under Obama — and sources familiar with the changes said this could leave the White House vulnerable to a “network compromise.”

OCISO staff are “systematically being targeted for removal from the Office of the Administration (OA) through various means,” the memo says. Those included “revocation of incentives, reducing the scope of duties, reducing access to programs, revoking access to buildings, and revoking positions with strategic and tactical decision making authorities.”

Meanwhile, others have left for different jobs. This includes Joe Schatz, the former White House chief information security officer (CISO), who left the post in August for a technology consulting firm.

Tom Kellermann, head cybersecurity strategist at VMware Carbon Black, served as a cybersecurity commissioner for the Obama administration. Under the Trump White House, “the Night’s Watch is very thin,” he wrote in an email to SDxCentral, referring to the military order in "Game of Thrones" that guards the wall to keep the Night Walkers out of the Seven Kingdoms.

“The administration has ostracized their own cybersecurity professionals,” Kellermann wrote. “The Night’s Watch is very thin. The termination of the cyber czar position compounded with placing individuals like [Rudy] Guliani in charge of cyber has created the perfect storm. We are under siege by an axis of evil in cyberspace and we must appreciate that American cybersecurity is tenuous as we fight an ongoing cyber insurgency.”