In this paper we present and validate a novel attacker model based on the \ economic notion that the attacker has limited resources to forge a new \ attack. We focus on the vulnerability exploitation case, whereby the \ attacker has to choose whether to exploit a new vulnerability or keep an old \ one. We postulate that most vulnerabilities remain unattacked, and that the \ exploit development cycle relates to software updates rather than to the \ disclosure of new vulnerabilities. We develop a simple mathematical model to \ show the mechanisms underlying our observations and name it ``The Work-Averse Attacker Model''. \ We then leverage Symantec's data sharing \ platform WINE to validate our model by analysing records of attacks against \ more than 1M real systems. We find the `Model of the Work-Averse Attacker' \ to be strongly supported by the data and, in particular, that: (a) the great \ majority of attacks per software version is driven by one vulnerability \ only; (b) an exploit lives two years before being substituted by a new one; \ (c) the exploit arrival rate depends on the software's update rate rather \ than on time or knowledge of the vulnerability.

In this paper we present and validate a novel attacker model based on the economic notion that the attacker has limited resources to forge a new attack. We focus on the vulnerability exploitation case, whereby the attacker has to choose whether to exploit a new vulnerability or keep an old one. We postulate that most vulnerabilities remain unattacked, and that the exploit development cycle relates to software updates rather than to the disclosure of new vulnerabilities. We develop a simple mathematical model to show the mechanisms underlying our observations and name it "The Work-Averse Attacker Model". We then leverage Symantec's data sharing platform WINE to validate our model by analysing records of attacks against more than 1M real systems. We find the 'Model of the Work-Averse Attacker' to be strongly supported by the data and, in particular, that: (a) the great majority of attacks per software version is driven by one vulnerability only; (b) an exploit lives two years before bein...