The FBI is responsible for, among other things, tackling fraud and corrupt practices in the public sector.

However, it seems the US federal agency may have its own problems with duplicity, after an investigation found that "a significant number of FBI employees engaged in some form of improper conduct or cheating" when obliged to sit a key exam.

Agents from the FBI – motto "Fidelity, Bravery, Integrity" – had to take the 90-minute assessment to prove they had understood guidelines on how to conduct terrorism investigations.

Suspicion was raised, however, when more than 200 employees completed the exam in less than 20 minutes.

The US justice department's subsequent investigation, despite being only "limited" in scale, found that 22 employees had employed dishonest means – ranging from conferring with others, using answer sheets, or taking advantage of a computer programming flaw to reveal the answers.

Although the number found to have cheated is small compared with the 20,000 FBI staff who took the test, the inspector general's office found that "the extent of the cheating related to this test was greater than the cases we detailed in this report".

The exam posed 51 questions on the Domestic Investigations and Operations Guide, introduced in 2008. Examinees were allowed to use the guide and notes during the test, but this was not enough for some.

Inspector general Glenn Fine found that even senior agents had abused the system, and documents one incident in which "three top managers" cheated. Two special agents took the test together, brazenly discussing questions and answers, while a particularly resourceful assistant director in charge (ADIC) was present.

"While the ADIC was also in the room at the time, he did not take the exam that day," Fine wrote. "Instead, the ADIC wrote down the answers and later used them to complete the exam another day."

The report does not name the ADIC, but the Washington Times named the person in question as Joseph Persichini Jr, who "retired in December in the midst of the investigation".

Perhaps there should be some sympathy for those convicted of cheating. The Huffington Post said that rather than merely being dishonest, FBI agents may actually have "mounted their own kind of internal protest, balking at the required 16-hour classroom training and in particular a 51-question multiple-choice open-book exam that by all accounts was poorly worded and difficult to understand".

Protest or not, it seems the FBI will have little sympathy with the cheats.

"We will follow up in each of the 22 cases the IG has found for disciplinary action, as appropriate, as well as any other allegations of misconduct," FBI director Robert Mueller said in a statement.