As some comments here confuse this with mass surveillance - this is the opposite:

“The monitoring of encrypted messages is to be carried out by installing a program in the computer system to be monitored, which exclusively extracts sent, transmitted or received messages either before encryption or after decryption.” This officialese describes the official plan of the Austrian federal government to buy malware and use it to monitor citizens who are not suspected of any criminal offense – if other investigative measures appear futile.

(Source: heise)

I personally have strong concerns that infecting the phones of the suspected persons is a reasonable approach. It’s probably extremely expensive, sponsors a doubious (at best) business model and if anything, can be used to find a drug dealer’s customers.