Focus falls on bitcoin trail in race to identify Twitter hackers

* Bitcoin wallets used after hack offer investigators clues

* Wallet involved linked to merchant service firms - Chainalysis

* Blockchain analysis increasingly used by law enforcement

By Tom Wilson and Anna Irrera

LONDON/NEW YORK, July 16 (Reuters) - Hackers who targeted some of Twitter's top users to reap bitcoin worth $120,000 have likely left digital footprints that could offer clues for law enforcement agencies investigating the attack, three blockchain analysis companies told Reuters.

In an unprecedented spree, the unidentified attackers on Wednesday hijacked the accounts of politicians, celebrities and billionaires, using them to solicit bitcoin transfers to a string of digital wallets.

A digital wallet used to consolidate the bitcoin has previously been linked with crypto firms including merchant service providers, U.S. blockchain forensics firm Chainalysis told Reuters - a clue that could aid investigators.

"They have interacted with service providers that have know-your-customer processes, and law enforcement can work with those service providers to find out who can be behind those accounts," spokeswoman Maddie Kennedy said, declining to give further details.

Twitter declined to comment. The Federal Bureau of Investigation, which sources told Reuters is leading a federal inquiry into the Twitter hacking, didn't immediately respond to a request for comment.

Bitcoin allows users to send and receive funds without revealing their personal identity. Yet its movements are recorded on the blockchain, a publicly viewable digital ledger that underpins the crypto currency.

By tracing illicit bitcoin to exchanges and crypto payment firms where identification is required, investigators can potentially pinpoint criminal suspects.

"In bitcoin it's very difficult to transact without leaving some clues on the blockchain," said Tom Robinson of Elliptic, a London-based blockchain analysis firm. One of the wallets used in the hack has transacted with exchanges in the past, he said.

Since 2016, blockchain analysis firms including Elliptic, Chainalysis and California-based Cipher Trace have won contracts with U.S. government agencies including the FBI and Drug Enforcement Administration, according to a database of U.S. government contracts https://www.usaspending.gov/#/search/83bba7bc5a719c1da25ff95d41c4349e. (Reporting by Tom Wilson in London and Anna Irrera in New York; Editing by Nick Macfie)