Following the discovery of the German Trojan program last year, many antivirus vendors added detection for it in their products, which most likely impacted the ability of law enforcement agencies to use it.

"If AV companies aren't in the loop on specific tools, they're going to detect them as some form of spyware (if they detect them at all)," David Harley, a senior research fellow at ESET, said Tuesday via email. "If law enforcement agencies do approach the security industry, the precise response will vary according to circumstances, but ignoring policeware by request is both ethically and technically problematic, because a security company can't usually tell whether a specific instance of the software is legitimate or not."

Harley believes the use of such tools is justified if done in a lawful manner. "It's analogous to wiretapping done in accordance with due legal process (e.g. where an appropriate warrant has been issued), and it's perfectly logical to employ people who are familiar - or can be trained to be familiar - with the technology," he said.

A spokeswoman from the BKA Press and Information Office declined to comment about the job posting.

(Loek Essers in Amsterdam contributed to this story.)