MessageLabs has released a new issue of its monthly intelligence report, which reveals interesting statistics of spam originating from client computers that are infected by botnets. Not surprisingly, most spam comes from Windows users, but Linux systems are five times more likely to be sending spam than Windows. And: There is virtually no spam that is sent from Apple Mac computers.
Lovebug virus illustration (c) MessageLabs
MessageLabs’ new report is littered with numbers and even if you find spam and statistics interesting, this report may be a bit too much for most of us. However, it is comprehensive and breaks spam down to the operating system level.
As for the general information, spam still accounts for nine out of ten emails (89.9%) sent, one in 341 emails contains malware and one in 455 emails carries a phishing attack. MessageLabs also said that it blocks 1675 malicious websites per day on average.
Botnets and their spam share in March 2010
Spam is dominated by botnets that infect client computers around the globe and use their connectivity to send out emails. Rustock is believed to be the largest botnet at this time, with up to 2.4 million infected computers that send more than 43 billion spam messages every day and account for almost 33% of all spam sent worldwide. Grum follows with about 1.2 million PCs and 32 billion messages per day and a share of 24%. The entire spam volume caused by all botnets currently monitored is about 121 billion messages per day from up to 5.6 million computers. Non-botnet spam is only 7 billion messages per day, bringing the total spam volume to just above 128 billion messages per day.
If we look at the PCs that are controlled by the botnets and that are sending the spam, and break them down by operating system, MessageLabs’ data shows, not surprisingly, that 92.65% of all spam came from Windows machines, 0.001% from Mac OS X systems and 5.14% from Linux computers in March2010.
The numbers are not that surprising, given Windows’ market share that is believed to hover around 90%, according to Net Applications. However, MessageLabs compared the installed base of an operating system with the actual number of spam messages sent to come up with a number that reveals the likelihood of a computer sending spam – and got an interesting result. This spam index gave Windows a number of 1.01 and Linux 4.99, which makes the operating system five times more likely to be sending spam than a Windows computer. MessageLabs estimated Windows to hold a market share of 91.58%, Mac OS X 5.33% and Linux 1.03%.
The company said that the results do not take into account that many owners of non-Windows machines may be using a virtual machine environment, running with a Windows OS subsystem, perhaps for email purposes. “In such cases they may not bother to take proper security precautions for the virtual machine environment. It is equally as important to safeguard a Windows virtual machine connected to the Internet as it is for any other environment; the fact that it may be running in a virtual environment is irrelevant.”
The conclusion of the MessageLabs report is that Windows is still the most attractive target for spammers. However, “it may be that Linux machines are equally as vulnerable, perhaps through drive-by attacks targeting vulnerabilities in browser plug-ins,” the company said.
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