It appears the United States Postal Service is determined not to be the courier of choice for drug dealers any longer.

Judging by a recent job listing sent to the information security community, the United States Postal Inspection Service (USPIS) — the law enforcement arm of the U.S. Postal Service (USPS) — wants to sniff out users of darknet markets that send their packages by mail. Applicants for the job, listed as “Investigative (Internet) Analyst”, are expected to know their way around bitcoin — the currency of choice on the darkweb — a as well as other tools typically used by darknets, like Tor.

Although the job listing doesn’t appear to be published online any more, according to Deep Dot Web the USPIS is specifically looking for applicants able to unmask pseudonymous users of dark net markets:

“Candidates shall be capable of performing a prioritized assessment of the data to identify the most critical and reliable data in order to identify bitcoins, locations, accounts, services, travels, email addresses, IP addresses and other pattern of life data in an effort to determine physical attribution of an Internet identity.”

And, according to Motherboard:

“The analyst shall be capable to use technology solutions to actively search, analyze and prioritize the various market places and cyber-criminals to identify high value targets for the USPIS investigators.”

Darknet markets are eBay-like market places that operate on darknets such as Tor and I2P, most commonly operating as digital black markets. The vast majority of purchases are illegal drugs, but weapons, stolen credit card details and other illegal goods are traded as well. Since pioneering darknet market Silk Road was closed down in 2013, and founder Ross Ulbricht sentenced to life in prison, buying and selling of illegal contraband has only increased.

Shipment of the illegal goods is exclusively done by mail. In most cases, at least in the United Stated, this is done with USPS. As a federal agency, USPS is bound by the Fourth Amendment of the US Constitution. This prevents the postal service from inspecting packages without a warrant, attaining which in turn requires probable cause. Providing this probable cause is — presumably — where the investigative analyst would come in.

That said, even now, the mailing system is probably the weakest link in darknet market operations. Where online communication is protected with encryption and Tor, and bitcoin (or monero) payments can be mixed and tumbled, packages still require physical addresses — and can be intercepted.

Indeed, the USPIS does already regularly provide assistance in darknet investigations. Perhaps most notably,  the USPIS is said to have played an active role November 2016’s “Operation Hyperion,” one of the most extensive police operations focused on the darknet to date, where thousands of users of darknet marketplaces were identified.

The job listing suggests the USPIS will ramp of these and similar efforts in the future.