The UK Defense Ministry said this in its daily intelligence update published on Twitter, according to Ukrinform.
"Analysis by Geollect indicates that since 14 May 2023, commercial vessels’ Automatic Identification System (AIS) data has been remotely spoofed to create the impression of a 65km long Russian pro-war Z symbol on the Black Sea, visible on open source tracking software," the update reads.
AIS is used to track vessels, including to ensure their safety. Tracks making up the image suggested vessel speeds of up to 102 knots (188 km/h), further suggesting they were fake.
According to the report, pro-Russian actors likely conducted the spoofing as an information operation, potentially in an attempt to bolster Russian morale ahead of an anticipated Ukrainian counter-offensive.
"The spoofing of AIS increases the risk of maritime accidents. Despite Russian virtual information operations in the Black Sea, its physical navy remains vulnerable: the Ivan Khurs intelligence gathering vessel was likely attacked on 24 May 2023," British intelligence said.
Ukrinform earlier reported that the Ivan Khurs, a Russian reconnaissance ship that joined the Russian Black Sea Fleet only in 2018, was attacked by unidentified unmanned surface vehicles 74 kilometers north of the Bosphorus Strait.