Malware has quickly evolved to take advantage of weaknesses in digital defenses. In 2012, more than 40 million Windows systems were infected with malware, according to data collected by Microsoft in its annual Security Intelligence Report. And Google researchers found that, of four common antivirus scanners, the best only detected 25 percent of real-world malware, and combined, the scanners only caught 40 percent of malicious downloads.
Malware writers have honed their technique to do well against current defenses, says Srinavas Kumar, chief technology officer of TaaSERA, a security-service provider.
"The malware writers know how to get around antivirus software," he says. "They can detect that antivirus is running or that IPS/IDS is watching and make it very difficult to blacklist them."
To defend against the latest attacks, enterprise security professionals need to know why today's malware is so successful. Culling data from a number of recent studies and discussions with security experts identifies five strategies for success.
1. Start with the old and sick.
Like a real-world pathogen, malware does best when the potential victim's immune system is compromised. Unpatched systems with out-of-date -- or no -- antivirus software have about a 1-in-80 chance of being infected in any given month, according to Microsoft's latest Security Intelligence Report. The same report found that the average fully-patched Windows systems running up-to-date antivirus had only a 1-in-500 chance of being infected.
"Although there is no such thing as a perfect security product, (our) findings ... clearly show that using real-time security software from a reputable vendor and keeping it up to date are two of the most important steps individuals and organizations can take to reduce the risk they face from malware and potentially unwanted software," Microsoft stated in the report.
Approximately 23 percent of all Windows systems are out-of-date, the company found.
2. Infect over real-time communications.
Infection vectors that give defenders the least time to react tend to produce the most compromises, according to a recent study of malware traffic by Palo Alto Networks. E-mail-borne malware was typically identified and a signature developed within 5 days, while attacks that used a more real-time medium, such as Web downloads, helped the malware escape detection for up to 20 days.
"When you move to things that are coming through a browser or live Internet connection, it reduces the amount of time the security software gets to analyze it," says Wade Williams, senior security analyst with Palo Alto. "With e-mail, the file sits there for a minute or two, so AV can give it the once over."
Palo Alto used data from the networks of more than 1,000 companies to analyze suspicious activity that had managed to slip pass firewalls and e-mail security gateways. Over three months, more than 68,000 files were determined to be malware samples, of which only 61 percent were detected by six popular antivirus programs, the company stated in its report
3. Wear a different face every time.
Polymorphism, where a malicious program is modified to escape detection by antivirus programs, used to be an advanced technique. Now, Trojans, bot software, and exploit kits are frequently "packed" or otherwise disguised on a regular basis to foil defenses.
"Attacks now try to never repeat the same sequence of activities twice," says TaaSERA's Kumar. "They will basically add such randomness that it won't be recognized by antivirus."
4. Lay low for a while.
Malware authors are increasingly adding a sleep feature to their programs that prevents the software from executing unless a certain amount of time has passed, or some user-activated event has occurred, such as a mouse click. The delay typically foils defenders' efforts to sandbox untrusted executables and test them for malicious behavior.
"There is actually a very strong effort by malware writers to evade a lot of defenses -- not just antivirus anymore -- but bypassing a lot of traditional sandboxing methods," says Rob Rachwald, senior director of market research FireEye.
In a recent analysis, FireEye found malware that waits for a user to execute a specific mouse command before running. "Given that automated analysis systems do not employ mouse commands, these programs lie dormant and undetected when inspected in sandboxes," the company states in the analysis.
[Malware writers go low-tech in their latest attempt to escape detection, waiting for human input -- a mouse click -- before running their code. See Automated Malware Analysis Under Attack.]
5. Hiding is half the battle.
Malware not only waits for the defenses to grow complacent, but actively hides itself in ways to avoid detection on systems running antivirus. In fact, more than half the code in a typical malicious program is code to bypass defenses, says Palo Alto's Williams.
"We saw more malware behavior that was dedicated to hiding from on-box security, than we saw hacking and data-theft behavior," Williams says. "A really large part of the malware's brain is focused on how to stay away from the security that Windows has, and how to stay away from the prying eyes of suspicious users."
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