Which of the following is an example of an inference attack?

An inference attack involves extracting sensitive information from the available data without direct access to that information. In the context of the choices provided, estimating a salary based on salary sorting exemplifies this concept well.

In this scenario, an employee might analyze publicly available salary data or general salary ranges associated with specific job titles or departments. By correlating this data with their own role and observations within the company, the employee can infer their own salary and possibly even the salaries of their coworkers. This is a classic example of an inference attack because the employee is making educated guesses based on limited information rather than having direct access to confidential salary data.

The other options do not represent inference attacks as effectively. For instance, simply finding an address by looking up a name is a straightforward search rather than an inference. Furthermore, a compromised password database is a direct breach of security where sensitive information is stolen outright. Lastly, filtering contacts from a political donation list by area code does not rely on inferred connections but rather on categorizing already collected and publicly available data.