The chief executives of McAfee, the antivirus software maker, and CNET, an online publisher, quit on Wednesday over Silicon Valley’s options backdating scandal.

Their departures are likely to increase fears that the apparently widespread practice could lead to a broader shake-up of senior leadership in the world’s leading technology hotspot.

The resignations come a week after Apple Computer cleared Steve Jobs, its co-founder and chief executive, of wrongdoing over options backdating, even though he was aware of the practice in “a few instances”.

Shares in McAfee rose 2.4 per cent after the company said it had appointed Dale Fuller, the former chief executive of Borland Software, to replace George Samenuk as chief executive.

Mr Samenuk said: “I regret that some of the stock options problems . . . occurred on my watch.” His departure followed news that the company would be required to restate its earnings by $100m to $150m to account for improper backdating.

McAfee said it had ousted Kevin Weiss, president, who joined the company in 2002 and became president in March, several years after improper backdating at the company began.

Mr Fuller declined to elaborate, noting that shareholders would be able to “read everything . . . in excruciating detail” in filings.

Shares in CNET, owner of the technology news website, dropped 6.5 per cent after the company announced the departure of Shelby Bonnie, its co-founder, chairman and chief executive. He resigned after an internal probe found the group backdated some options grants between 1996 to “at least” 2003.

Mr Bonnie said he was “deeply disappointed” that backdating occurred under his leadership.