South Carolina inmates managed to blackmail 442 U.S. service members from across the Army, Navy, Air Force, and Marines out of more than $560,000 as part of a sprawling sextortion ring, Naval Criminal Investigative Service officials announced on Wednesday.

The NCIS announcement, which marks the end of the first phase of the multi-year Department of Defense joint investigation dubbed 'Operation Surprise Party,' found that South Carolina inmates "used various social media platforms and dating sites posing as a female, exchanging pictures with service members" in a practice known as catfishing, according to NCIS.

"After the service member responded, prisoners would then assume a role of the female's father, who claimed the female was a juvenile," NCIS explained in a new release. "Prisoners would also assume the role of a police officer or someone in a position of authority, demanding money, on behalf of the family, in exchange for not pursuing charges through law enforcement channels."

The existence of the investigation was first revealed in an Army Criminal Investigation Command warrant submitted to a federal court on Oct. 3, but the scope and scale of the sextortion ring were previously unreported.

According to NCIS, more than 250 people "are being investigated and face potential future prosecution" for their role in the scam, ranging from guests of the South Carolina Department of Corrections to "outside civilian associates."

"We do to 10-12,000 felony investigations annually and we see all kind of things, but this is a different sort of crime," Army CID public affairs chief Christopher Grey told Task & Purpose. "The players, the circumstances are different than the normal felonies we deal with."

CID had previously cautioned soldiers to be on guard for sextortion scams where criminals “use any dishonest method to make contact with potential victims and then attempt to blackmail them," as Special Agent Daniel Andrews, head of CID’s Computer Crime Investigative Unit, said in an Army release. “To avoid falling prey to a sextortionists never send compromising photos or videos of yourself to anyone, whether you know them or think you know them."

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