Collected research

Stiltwalker, exploits weaknesses in the audio version of reCAPTCHA

Defcon Group 949

Stiltwalker defeats audio CAPTCHAs with machine learning: an amplitude splitter cuts a challenge into single utterances, then a neural network plus MD5 and pHash lookup tables solve them. Successive rounds scored 99.1% and 60.95% against reCAPTCHA, and later versions reached 56-99% against Nucaptcha, PayPal, SecurImage, Slashdot and Davids Summer Communication.

Record

Document

Defcon Group 949

Published by

dc949.org

Topic

Other

In the archive

• Collected in the 2012 research round

Related sources

• Stiltwalker — BsidesLV 2012 slides
• Stiltwalker — BsidesLV 2012 presentation bundle
• Stiltwalker — LayerOne slides
• Stiltwalker — LayerOne presentation bundle

Tags

• auth-bypass
• tooling
• filter-bypass
• case-study
• owasp-a01-2021
• owasp-a05-2021

This page is the archive's own catalogue record. The research is the work of dc949.org, first published at the original source. Preserved copies are kept so the citation survives its host; this one was last captured on 10 August 2026.