RSA helps companies confirm user IDs and manage other digital security risks. It serves 30,000 customers ranging from banks to consumer-goods makers. It also runs security conferences, including one scheduled for this month in San Francisco that IBM dropped out of recently. The sale, rubber stamped Tuesday, was made to a consortium led by STG Partners, a private equity investor that specialises in tech; Ontario Teachers' Pension Plan Board; and Dutch private equity group, AlpInvest Partners.