A secret FBI hacking tool, used to compromise the Tor anonymous browser in one investigation, is facing challenges from criminal defendants, perhaps putting its future in doubt.
Defendants have demanded to see details of the FBI network investigative technique (NIT), the agency's name for the relatively recent hacking tool, in a handful of criminal cases, but the agency has refused to disclose the information.
A judge in a high-profile child pornography case, in which a website called Playpen was accessible only through Tor, is trying to decide whether the FBI should disclose the NIT"s source code to the defendant.
If the FBI shares the source code, its hacking tools may be compromised in future cases, but the U.S. Constitution's Sixth Amendment gives the defendant a right to confront his accusers and challenge their investigation.
Judge Robert Bryan of the U.S. District Court for the Western District of Washington wrestled with the competing interests in a case status order he issued in the U.S. v. Michaud case last week.
The defendant's request for the NIT source code "places this matter in an unusual position," Bryan wrote. "What should be done about it when, under these facts, the defense has a justifiable need for information in the hands of the government, but the government has a justifiable right not to turn the information over to the defense?"
Ars Technica, which reported on Bryan's order last week, noted that two other judges, in Oklahoma and Massachusetts, have ruled this year to suppress NIT-obtained evidence. And a defense attorney in West Virginia has filed to withdraw a guilty plea in a case involving NIT evidence.
In another order last week, Bryan refused Mozilla's request for the government to disclose the vulnerability in Tor. Tor is based on Mozilla's Firefox browser.
The ability of defendants to confront the evidence against them is "absolutely essential" to conducting fair trials, Wessler said. Secret evidence is "irreconcilable" with the U.S. justice system, he added.
The FBI has defended NITs, saying their use is limited. "The use of Network Investigative Techniques is lawful and effective, and only employed when necessary -- against some of the worst offenders," the agency said in a statement. "The technique is time and resource intensive, and is not a viable option for most investigations ..."
The Michaud case raises several sticky issues, technology and legal experts said.
Both sides should have access to evidence in a criminal case, but FBI disclosure of the NIT's source code could kill the tool's effectiveness going forward, said Paul Fletcher, security evangelist for security vendor Alert Logic.
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