The Detekt software was needed as standard anti-virus programs often missed spying software, it said.
Amnesty said many governments used sophisticated spying tools that could grab images from webcams or listen via microphones to monitor people.
It wants to see more regulation of the spying software used by governments.
“These spying tools are marketed on their ability to get round your bog-standard anti-virus,” said Tanya O’Carroll, an adviser on technology and human rights at Amnesty International.
The makers of spying software did extensive testing to ensure that the way they infected and lurked on a computer did not trigger security alerts, she added.
A free tool released Thursday allows users to scan their computers for surveillance malware that has been used in attacks against journalists, human rights defenders and political activists around the world.
The open-source tool, dubbed Detekt, was developed by security researcher Claudio Guarnieri. It was released in partnership with Amnesty International, Digitale Gesellschaft, the Electronic Frontier Foundation and Privacy International.
Detekt scans computers for infection patterns associated with several families of remote access Trojans (RATs): DarkComet RAT, XtremeRAT, BlackShades RAT, njRAT, FinFisher FinSpy, HackingTeam RCS, ShadowTech RAT and Gh0st RAT.