Due to a small typing error, millions of emails from the US military were unintentionally forwarded to Mali, a Russian ally.
For years, emails meant for the US military's ".mil" domain have been transmitted to the west African nation with the ".ml" extension.
According to reports, some of the emails contained private information including passwords, medical information, and high officers' travel schedules.
The Pentagon claimed to have taken action to resolve the situation.
The Financial Times, which broke the story, claims that Dutch internet entrepreneur Johannes Zuurbier discovered the issue more than ten years ago.
He has held a contract to handle Mali's national domain since 2013 and has apparently collected tens of thousands of misdirected emails in recent months.
None were tagged as classified, but they included medical data, maps of US military bases, financial records, and planning documents for official trips, as well as some diplomatic letters, according to the newspaper.
This month, Mr Zuurbier issued a letter to US officials to raise the alarm. He stated that his contract with the Mali government was about to expire, implying that "the risk is real and could be exploited by US adversaries." On Monday, Mali's military administration was set to take control of the domain.
According to current and former US officials, "classified" and "top secret" US military communications are routed through separate IT networks, making it unlikely that they will be accidentally compromised.
However, Steven Stransky, a lawyer who previously served as senior counsel to the Department of Homeland Security's Intelligence Law Division, believes that even seemingly innocuous material could be beneficial to US adversaries, especially if it includes specifics on individual employees.
"Those sorts of communications would mean that a foreign actor can start building dossiers on our own military personnel, for espionage purposes, or could try to get them to disclose information in exchange for financial benefit," Mr Stransky explained. "It's certainly information that a foreign government can use."
Lee McKnight, a Syracuse University professor of information studies, believes the US military was lucky that the issue was brought to its attention and that the emails were directed to a domain used by Mali's government rather than cyber criminals.
He went on to say that "typo-squatting" - a sort of cybercrime that targets individuals who misspell an internet domain - is rampant. "They're hoping that a person will make a mistake, and that they can lure you in and make you do stupid things," he noted.
Both Mr. McKnight and Mr. Stransky believes that human errors are a major concern for IT professionals working in government and the private sector alike.