The Australian arm of Allen & Overy risks losing trust with clients and the public if it stays silent on the cyberattack the international legal firm suffered last week, the former boss of the government’s cybersecurity agency said.

Alastair MacGibbon, the former head of the Australian CyberSecurity Centre and an adviser to two prime ministers, told The Australian Financial Review that “the fact [Allen & Overy] is not making any comment is unhelpful”.