The recent breach of email service provider Epsilon put as many as fifty major companies, including Citibank, Verizon and Disney, as well as their thousands of customers at risk providing cyber criminals with access to personal details.

The targeted phishing attacks, alias spear phishing, made use of fake yet personalized e-mails to hoax customers into revealing their personal information such as names, e-mail addresses and financial details.

The breach put questions on the security measures employed by the company that is entrusted with sending around 40 billion e-mails a year. According to Epsilon, the attack hit two per cent of its clients.

Attackers may use the stolen data to craft some convincing e-mails to befool the targeted people with an unprecedented ease.

Later, Epsilon assured customers that no other customer information was compromised. But, the already stolen names and e-mails addresses could be used by cyber criminals to trick people into clicking on malicious links, download malware and responding to requests for account numbers and passwords.