Commodity malware versus custom exploits

In my post about e-card Trojans, I mentioned that I hoped to flesh out my thoughts on malware as compared to more customized exploits. As we all should know from numerous stories, commodity malware is big business. Malware is increasingly used to steal information to turn a profit, and is likely being used to target information that is valuable in other ways. So my question is, in a world where the U.S. military has to ban USB drives to combat malware, how much trouble are customized private exploits actually worth?

There are certainly advantages to customized private exploits, but when a spammer only needs one response for every 12.5 million emails sent to be profitable, it seems that the economics of the situation may favor the lower cost of slightly modifying malware to bypass anti-virus software and then blasting away with malicious emails, advertisements, and other links.

A customized exploit that is only being used by a small number of people should obviously be more difficult to detect. However, when anti-virus and traditional IDS rely so thoroughly on signatures of known activity, the question is really about how difficult the attacker needs detection to be. In many cases, it may not be worth using a skilled attacker to craft a specific exploit when said attacker could be increasing the efficiency of more voluminous attacks.

Of course, this is not really an 'either' 'or' situation. Both types of attacks can effectively be used, and when combined they are probably both more effective. Sow mass confusion and panic with widespread malware attacks while performing more targeted attacks for particularly desirable information. Those playing defense will likely be busy scurrying after the malware while the targeted attacks fly in under the radar, especially in these economic times where security operations may be suffering from budget cuts.

I also don't mean to downplay the skill it takes to enumerate network services and write a custom exploit for one or more of those services on the spot. Relatively few people can do that, I am certainly not one of them, and in many cases it is virtually undetectable. At the same time, I often feel that those talented exploit writers and penetration testers give too little credit to the effectiveness of common malware. It seems to me that commodity malware has become quite effective at generating revenue and stealing information.

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