Hillary Clinton’s BlackBerry was vulnerable to hackers during her first visit abroad as secretary of state, according to internal State Department documents obtained by the Washington Free Beacon.

State’s top diplomatic security official warned Cheryl Mills, Clinton’s chief of staff, against using their BlackBerries in "Mahogany Row," the suite of offices at the department’s Foggy Bottom headquarters where the secretary and her top deputies worked, in a March 2009 memo.

"I cannot stress too strongly … that any unclassified BlackBerry is highly vulnerable in any setting to remotely and covertly monitoring conversations, retrieving emails, and exploring calendars," wrote Eric Boswell, who led State’s Bureau of Diplomatic Security.

Clinton’s BlackBerry was not issued by the State Department, according to former spokeswoman Jen Psaki. The Democratic presidential frontrunner received messages to her personal email address on the device. Hundreds of emails sent to that address contained information subsequently deemed classified.

According to internal emails about Boswell’s memo, released with significant redactions to the Competitive Enterprise Institute in response to an open records request, intelligence suggested that Clinton’s BlackBerry was vulnerable to monitoring or intrusion during her first trip abroad as secretary of state.

A redacted sentence in the memo "indicates [that State’s diplomatic security division] have intelligence concerning this vulnerability during her recent trip to Asia," according to an email from Boswell’s executive assistant.

Clinton told Boswell that she "gets it," according to that email. However, Clinton has also said that she used a personal email address instead of an official government one so that she could receive emails on her BlackBerry.

At least 300 of those emails contained information that has since been deemed classified. Clinton says they were not marked as such at the time, but the nondisclosure agreements she signed upon taking the job made her responsible for ascertaining the classification status of information in her possession.

Boswell’s memo shows that State Department cybersecurity officials were concerned from the beginning of her tenure as secretary about the use of BlackBerrys by Clinton and her senior staff.

"Our review reaffirms our belief that the vulnerabilities and risks associated with use of Blackberries in the Mahogany Row [redacted] considerably outweigh the convenience their use can add to staff that have access to the unclassified OpenNet system on their desktops," Boswell wrote.

OpenNet is State’s computer network linking unclassified workstations in its Washington. D.C., headquarters with embassies and other offices around the world.

According to an internal email on Boswell’s memo, "the Secretary does not have an OpenNet+ terminal (because she doesn’t use computer systems)."

Despite the vulnerabilities identified in the memo, Clinton continued using her BlackBerry during her tenure as the nation’s chief diplomat. Clinton’s use of the device became an Internet meme in October 2011 after a photo of her wearing sunglasses while typing on a BlackBerry went viral.

Boswell’s memo contained guidance for Clinton should she decide to continue the use of BlackBerrys in spite of the risks, but that guidance was redacted from the version released to CEI.

Clinton's campaign did not a return a request for comment.