The companies anticipate that the move will provide online traders with a powerful UK-based fraud protection service.
"E-commerce figures suggest that 95 per cent of all online fraud detected involves more than one retailer. It is clear from this figure that the way forward for web traders is to share their data," said Paul Simms, chief executive at The 3rd Man.
Early Warning UK was set up by internet fraud victim Andrew Goodwill in 2002, and provides fraud-busting services to a wide cross-section of online retailers.
The service allows traders to post details of actual or attempted internet crimes, and to find out whether others have had similar experiences. Fraudsters are subsequently exposed through a network of data sharing.
The 3rd Man provides fraud screening services to over 18,000 retailers, claiming to save them in excess of £10m a month.
The firm also operates SuperSearch, a national card-not-present fraud file which enables retailers to share and monitor information on high risk transactions deemed to be fraudulent.
"By bringing Early Warning under The 3rd Man umbrella our aim is to develop a massive and dynamic system of information sharing for retailers to protect themselves and their genuine customers," said Simms.
"The ability to share fraud data with Early Warning and learn from their experiences is a major boost in the fight against card crime."
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