What is RoundUp Torrential Downpour?

RoundUp Torrential Downpour is a law-enforcement investigative BitTorrent client used in peer-to-peer (P2P) cases. It is commonly described as a tool that connects to BitTorrent like a normal peer and produces run artifacts (logs/exports) that investigators later use in reports and affidavits.

Quick definitions (so everyone is talking about the same thing)

What it does (in plain English)

In a typical BitTorrent case workflow, investigators use the tool to find a peer participating in a specific torrent, connect to that peer, and record protocol-level identifiers (such as the torrent identifier and peer session identifiers). In some workflows, the tool is also used to retrieve data under conditions investigators describe as a controlled or “single-source” download.

Does Torrential Downpour hack my computer?

No. In the typical description, the tool does not install software on a target computer or “break in.” Instead, it connects to a public-facing BitTorrent endpoint and requests data the peer is offering on the network. BitTorrent is designed for sharing; it is not designed to be private.

What “single-source download” usually means

When an affidavit uses the phrase “single-source download,” it is usually making a conditions claim: investigators say they restricted the download so that data was obtained from one specific target IP:port (rather than from multiple peers in the swarm). This is a powerful claim when it is real and documented—so it is also a claim you should verify against the run artifacts.

What records matter (what to ask for in discovery)

The most important question is usually not “what can the tool do,” but “what does the record show happened in this case?” If your case turns on tool output, focus early on obtaining the run artifacts that let you audit the narrative.

Start here:

Is this a Fourth Amendment “search”?

In many jurisdictions, courts treat BitTorrent downloads of publicly shared data as accessing what was exposed to the public, not searching private files. That does not mean every motion is hopeless; it means you often get more leverage from case-specific defects (overstatements, staleness, nexus, scope, and documentation gaps).

For a lawyer-friendly overview, see: Torrential Downpour and the Fourth Amendment.

Can I get a copy of the software?

Generally, no. Defendants and experts have often been restricted to limited review arrangements (if any) rather than obtaining a distributable copy. In litigation, the practical focus is usually on the artifacts from the specific run and what they prove.

Continue reading (the fastest path to understanding the evidence)

Can you help me?

Yes—if you are defense counsel or part of law enforcement, please contact me. I intentionally limit my services to avoid enabling the distribution or possession of CSAM in any way.

Not legal advice. This page is for informational purposes and does not provide legal advice. Every case turns on specific facts and controlling law in your jurisdiction. Work with qualified counsel and, where appropriate, a qualified expert.

External references

BitTorrent & Digital Contraband
Strengthening Forensic Investigations of Child Pornography on P2P Networks
United States v. Gonzales