Attachment spam – the latest trend

Spammers using common file formats as attachments for pump-and-dump scams - by GFI Software

This white paper explains what makes spam such an unbearable problem and how spamming tactics are evolving daily to beat anti-spam software. In the space of two months, spammers have switched from image spam to using PDF, Excel and ZIP file attachments. By using these attachments to send images instead of embedding them in the body of the email message, spammers have taken the cat-and-mouse game with anti-spam software developers to a new level.

At one point or another – like the majority of computer users – you have received emails that promise business deals worth millions of pounds, that try to sell products to improve your appearance or that try to convince that it’s worth investing your money in a particular company or stock. Dealing with spam (unsolicited email that is not targeted at specific individuals), is one problem that all email users share in common. Research shows that between 65% and 90% of all email received is considered spam.
On an individual user basis, spam is annoying; it is a waste of time and often contains spyware, malware and even pornography. On a company-wide basis, the same threats apply however there is also the financial cost to manage spam that must be taken into consideration.

The evolution of spam

Until a while ago, spam was the domain of text- or html-based emails. For anonymous delivery, these messages traditionally relied on abusing open SMTP relays. When open SMTP relays became less common, spammers switched to proxy servers, dial-up services and more recently, hijacked computers. Spammers designed personalized template emails to deliver their messages and then made use of bulk mailing software for distribution.
To block spam, email service providers and companies often relied on keyword ‘detection’, and drew up a list of keywords that commonly appeared in most of the spam email. This list would often include keywords such as ‘viagra’ or ‘bank’. However, this method often blocked genuine email and adding more keywords simply resulted in more false positives which in turn blocked legitimate email. But spammers became smarter too, and they addressed keyword blocking by replacing keywords such as ‘viagra’ to ‘v1agra’.
Another attempt at blocking spam includes making use of blacklists that contain a list of IP addresses of known spammers or compromised hosts. However, these lists have to be constantly updated because spammers have learnt to counteract this by rapidly changing the origin of spam.

New trends: Dynamic Zombie botnets

Botnets can be defined as networks of compromised computers which can be controlled by a single master.

Sign up for ITworld's Daily newsletter
Follow ITworld on Twitter @IT_world

• Email
• Print
• Share
  • Slashdot
  • Digg
  • Stumble
  • Reddit
  • Newsvine