BUZZ — Varonis rises after Proofpoint agrees to $6.3 bln takeover
* Shares of Varonis Systems rise 2.4% to $48.50 premarket * Private equity Thoma Bravo-owned Proofpoint said to buy the data security firm in $6.3 bln all-cash deal * Offer values VRNS at $49.75/share — 52% premium over close on June 22, the day before speculation about possible sale emerged * Deal expected to close in