TDS, a mid-ranging ISP in the US, has had a hellish week, mainly because of a series of major phishing attacks on its subscribers, who have been swamped with spam email that appears to come from admin accounts on the TDS network.
The volume of email has, at times, brought the TDS email system to a grinding halt, creating the email equivalent of a distributed denial of service on its servers.
Perhaps worse, many customers were responding in anger to the phishing emails, which gives the hackers an indication that they're hot valid email addresses.
Early indications suggest that users who replied where then swamped with more `admin' email from `TDS' but the ISP hasn't confirmed or denied this.
Systems are back to normal today after the ISP triggered a cleansing system on its email servers, stripping out so-called `admin' email, but some spam is still reported to be trickling through from outside the TDS network.
TDS says it identified six different phishing e-mails, a couple of which look "kind of authentic," a spokesperson said.
The ISP says that telltale signs of a phishing e-mail include "making immediate demands for information, spelling mistakes, and grammar mistakes..."