According to a New York Times report, ToTok "is used by the government of the United Arab Emirates to try to track every conversation, movement, relationship, appointment, sound and image of those who install it on their phones.
According to the US officials familiar with the classified intelligence assessment, the App that works like Signal or Telegram has been downloaded millions of times on Android and iOS devices in the Middle East, Europe, Asia, Africa and North America.
"ToTok surged to become one of the most downloaded social apps in the United States last week, according to App rankings and research firm App Annie," the report said on Monday.
An investigation by NYT found that the firm behind ToTok is known as Breej Holding which is a front firm affiliated with DarkMatter, an Abu Dhabi-based cyberintelligence and hacking firm.
DarkMatter is already under an FBI investigation for possible cybercrimes.
The probe also linked ToTok to Pax AI, an Abu Dhabi-based data mining firm that appears to be tied to DarkMatter.
The UAE "has also been at the forefront of using surveillance technology to crack down on internal dissent, including hacking Western journalists, emptying the banking accounts of critics, and holding human rights activists in prolonged solitary confinement over Facebook posts", the report claimed.
The UAE government declined to comment on the report.
( With inputs from IANS )