Israeli ad technology firm Discover-Tech has been found to have conducted large-scale ad bidding targeting users of SpaceX's satellite internet service Starlink. Security experts raised the possibility it was not routine ad buying but activity aimed at determining users' locations and monitoring them.

On Oct. 28 (local time), Japanese IT outlet Gigazine reported that TrendAI, part of security firm Trend Micro, said in a recent report it found abnormal ad bidding activity targeting Starlink users.

TrendAI classified the activity under the codename SHADOW-EARTH-79. The report did not name the company, but Reuters cited 6 people familiar with the research as saying Discover-Tech was the firm involved.

Ad bidding records analysed by researchers showed concentrated targeting of specific countries. In Hungary, 64,218 of 70,500 bid-related records, or 91.1 percent, were linked to the firm. In Israel, 123,396 of 136,917 records, or 90.1 percent, were linked to it.

The firm also accounted for a large share of Starlink traffic. During the analysis period, 66,208 ads shown to Starlink users were linked to Discover-Tech, or 12.9 percent of the total. That was the second-largest volume after U.S. advertising company SteelHouse.

In particular, Discover-Tech appeared as the top winning bidder in Starlink-related ad auctions in 105 countries. They included Syria, Sudan, Myanmar and Libya, where Starlink use is banned or restricted.

The issue is that real-time online ad auctions can pass users' IP addresses, device information and location-related data to advertisers. Researchers said combining such information could be abused to infer users' identities or track their movements.

Discover-Tech has also been identified as a company linked to the zero-click spyware attack AdFection, which infects devices through online advertising. Still, the Starlink ad auction records alone do not confirm actual user monitoring or spyware infections.

After the investigation, Google and Comcast, among others, blocked Discover-Tech's access to their advertising platforms. Discover-Tech and SpaceX did not respond to requests for comment on the related reports.