Verizon customers this week received email informing them that their personal contact information had been compromised as part of the expansive attack against Epsilon.Verizon was one of 50 companies whose customer email information had been stolen as part of the massive hack on Epsilon, an email service provider. Other victimized companies include Target, Citibank, J.P. Morgan, Marriott and Best Buy. And like those other companies, Verizon also sent out an email to its customers informing them that Epsilon had assured them that "the information exposed was limited to email addresses, and that no other information" was exposed.Epsilon first began alerting its client businesses about the email hack last week, when it acknowledged that an unknown hacker had gained access to customer email addresses. The company provided additional details at the start of this week, admitted that "approximately 2% of total clients" were impacted by the hack. In all, Epsilon counts around 2,500 businesses as its clients.Companies impacted have warned their customers to expect additional spam, malware and phishing attacks to pop up in their mailboxes. Best Buy, for instance, told customers to not respond to any email asking to confirm credit card information, even if the email appeared to come from Best Buy. Chase, meanwhile, advised customers to not respond to any emails "threatening to close your account if you do not take immediate action providing personal information." It also advised customers to not use their email addresses as personal login IDs or passwords.So far, Epsilon has failed to provide a complete list of companies whose records have been compromised, although combined tallies compiled by the IDG News Service and Network World have accounted for more than half of them.Read more about wide area network in Network World's Wide Area Network section.