British Airways' air-miles accounts, the coding site GitHub and the work chat service Slack have all been targeted in the latest wave of cyber-attacks.
The firms have informed their users of the incidents, reported the BBC.
Complaints about points being stolen from the BA's Executive Club scheme date back at least a fortnight.
One user said that their account had been used by someone to book a hotel room in Spain, while others claimed that their list of transactions showed "ex-gratia" deductions that had wiped out their entire credit.
A spokesman for the British Airways said that it believed that only "a small number" of its frequent flyers were affected.
