A slide from the presentation, which was widely circulated online this week after it was posted on a Facebook group page, showed the former secretary of state beneath photos of Chelsea Manning, Edward Snowden, Gen. David Petraeus and Nidal Hassan under the headline: "Who is the threat? Insiders."
"We have confirmed that the slide was developed 18 months ago and used locally as a part of a training presentation on best practices for handling classified material and maintaining operational security," the US Army Training and Doctrine Command said in a statement. "As is common with Army training requirements, the local unit was given latitude to develop their own training products to accomplish the overall training objective."
"This particular presentation had not been reviewed or approved by the unit's leadership, and does not reflect the position of the Army," the statement continued. "The training presentation has since been removed."
The slide was used at Fort Leonard Wood in Missouri, according to reports.
Clinton's inclusion would appear to be inspired by her use of a private email server during her four years at the State Department. While FBI Director James Comey said in July that Clinton's actions were "extremely careless," he recommended that no criminal charges be brought against her and none were.
The slide identified a handful of "careless or disgruntled employees" as examples of an insider "threat."
Manning, a former Army private, is serving a 35-year prison sentence for providing classified documents to Wikileaks, while Snowden, a former National Security Agency contractor, fled to Russia after leaking top secret documents in 2013. Hassan, a US Army major, was responsible for the 2009 massacre at Fort Hood, Texas, that left 13 people dead.
Petraeus, the former Army general and CIA director, pleaded guilty last year to mishandling classified information. He was sentenced to two years probation and fined $100,000. The slide also included a photo of Aaron Alexis, the gunman behind the 2013 Washington Navy Yard shooting that killed 12 people.
The Clinton campaign did not immediately respond to a request for comment.