I would challenge the concept of the government carrying out "legitimate surveilance" through this dubious means.

The person surveiled has not been has not convicted of a crime yet the state has taken onto itself to install software that would leave the person open to further hacking by random individuals.

This is akin to the police not simply breaking into the house of a man they suspected of a crime but also them leaving his door a-jar after they left. See the Sony Rootkit.