Improving Web Application Security: Threats and - CGISecurity

46 Part I: Introduction to Threats and Countermeasures●●●Vulnerability. A weakness in some aspect or feature of a system that makes athreat possible. Vulnerabilities might exist at the network, host, or applicationlevels.Attack (or exploit). An action taken by someone or something that harms an asset.This could be someone following through on a threat or exploiting a vulnerability.Countermeasure. A safeguard that addresses a threat and mitigates risk.Consider a simple house analogy: an item of jewelry in a house is an asset and aburglar is an attacker. A door is a feature of the house and an open door represents avulnerability. The burglar can exploit the open door to gain access to the house andsteal the jewelry. In other words, the attacker exploits a vulnerability to gain access toan asset. The appropriate countermeasure in this case is to close and lock the door.How to Use This ChapterThis chapter outlines a generic process that helps you identify and document threatsto your application. The following are recommendations on how to use this chapter:●●●Establish a process for threat modeling. Use this chapter as a starting point forintroducing a threat modeling process in your organization if you do not alreadyhave one. If you already have a process, then you can use this as a reference forcomparison.Use the other chapters in this guide to familiarize yourself with the mostcommon threats. Read Chapter 2, “Threats and Countermeasures,” for anoverview of common threats that occur at the network, host, and applicationlevels.● For more specific threats to your network, see “Threats and Countermeasures”in Chapter 15, “Securing Your Network.”● For more specific threats to your Web server, application server, and databaseserver, see “Threats and Countermeasures” in Chapter 16, “Securing Your WebServer,” Chapter 17, “Securing Your Application Server,” and Chapter 18,“Securing Your Database Server.”● For more specific threats to your assemblies, ASP.NET, serviced components,remoted components, Web Services, and data access, see “Threats andCountermeasures” in Chapter 7, “Building Secure Assemblies;” Chapter 10,“Building Secure ASP.NET Pages and Controls;” Chapter 11, “BuildingSecure Serviced Components;” Chapter 12, “Building Secure Web Services;”Chapter 13, “Building Secure Remoted Components;” and Chapter 14,“Building Secure Data Access.”Evolve your threat model. Build a threat model early and then evolve it as you go.It is a work in progress. Security threats evolve, and so does your application.Having a document that identifies both what the known threats are and how theyhave been addressed (or not) puts you in control of the security of yourapplication.