Criminals are taking advantage of Skype's 256-bit encryption and the internet's unpredictable routing scheme to set up drug deals and other crimes, say Swiss law enforcement officials.
According to swissinfo, a Swiss Broadcasting Corporation company, local police are investigating dozens of drug-related cases where Skype has been the medium of communication between gang members and client.
"Criminals know that the police have difficulties monitoring Skype," it quotes a Zurich prosecutor of drugs and organised crime, Christoph Winkler, as saying.
According to Bernhard Weder, head of a Swiss federal working group that is researching how to monitor internet phone calls, Skype is "extremely cleverly built", it said.
Weder believes Skype can decode calls, but said the firm has not been co-operative, a charge the company's PR agency denied.
Read more on Voice networking and VoIP
FBI planned a sting against An0m cryptophone users over drinks with Australian investigators
FBI arrests distributors accused of selling An0m encrypted phones to crime groups
Police raids around world after investigators crack An0m cryptophone app in major hacking operation
Secrecy around EncroChat cryptophone hack breaches French constitution, court hears