** Shares in France's Thales TCFP.PA fall 3.4% after a media report said that French defence firm Naval Group, where Thales holds a stake, is investigating a cyber leak
** The hackers claim to have accessed 1 terabyte of sensitive data regarding Naval Group's submarines and frigates, and have published 30 gigabytes of information in a forum, the Financial Times reported on Sunday
** This could affect Thales, which owns a 35% stake in Naval Group, says Jefferies
** The French government owns a 62.25% stake in Naval, according to the company's website
** Other European defence equipment makers also fall after the EU agreed on a trade deal with the U.S. including "hundreds of billions of dollars" of arms purchases
** Rheinmetall RHMG.DE and Leonardo LDOF.MI slip more than 1%, Renk R3NK.DE and Saab SAABb.ST fall around 2%
** By 0819 GMT, Thales is at the bottom of France's CAC40 index .FCHI and among top losers on the pan-European STOXX 600 index .STOXX which rises 0.7%
** Including Monday's fall, it has gained more than 67% YTD
(Reporting by Alessandro Parodi, additional reporting by Paolo Laudani)
((Alessandro.Parodi@thomsonreuters.com;))