By Daniel Hunter

Three quarters of businesses are leaving themselves open to security breaches from former employees, according to a cyber security expert.

IS Decisions found that only 24% of companies follow strict post-employment processes to ensure that employees no longer have access to company-sensitive information once they have left.

This major security oversight tallies with research from the employees' perspective conducted by IS Decisions in 2014, which found that over a third of users are still aware of having access to systems – with nearly 1 in 10 regularly accessing systems after having left the company.

François Amigorena, CEO of IS Decisions, said: “It’s often easy for companies to overlook post-employment processes when they’re worrying more about the behaviour of current employees.

“However, an employee on the outside with access to your systems can be as dangerous as any hacker or virus – and often your threat detection systems won’t pick up a former employee because it thinks the employee has genuine authority to access systems.

“Threats can go undetected for months, leaving a huge open window for attack. A simple employee exit checklist can help mitigate these threats.”