Pro PHP Security: From Application Security Principles to the Implementation of XSS Defenses, Second Edition

Security Issues Related to Shared Hosting

Every shared server must use virtual hosting techniques to allow many different users to run many different applications using shared hardware and software. The main problem with this arrangement is the “nobody's business” problem. Let us explain that name, in case you're not familiar with it. On Linux servers, programs can't run except under the ownership of a user. Some users may be individuals with accounts, in which case they are subject to the restriction of user privileges, or security profiles (which we discussed in Chapter 10). Other users may be administrative, existing simply to provide ownership for a variety of daemons, or processes that run, typically rather independently, in the background ...