Security Basics: Managing User Accounts

This post is one in a series of blog posts on the fundamentals of an information security program. You can see the complete list of posts in this series here.

At their most basic, cyber security breaches are characterized by unauthorized access. However, that unauthorized access is usually carried out by leveraging the access rights of one or more authorized users. It might be hackers on the other side of the world gaining access to a user's PC via a browser vulnerability and abusing the user's account to find and steal data around the network to which that user has access, whether intentionally or not. Or it might be an insider or disgruntled former employee abusing their legitimate (or formerly legitimate) account to gain access to things to which nobody ever intended them to have access.

Ensuring that user accounts are created with appropriate access rights, that access is removed when no longer needed, that when new accesses are granted only the necessary access is granted, and that accounts are disabled and/or removed when no longer needed are essential, basic functions of IT housekeeping that are all too often not handled in a thorough and systematic way. Organizations typically have accounts hanging around that are no longer valid, and almost every organization often grants users access to files, folders, applications, systems, and databases beyond what the user truly needs to do their job. But below I want to focus on the risk associated with unneeded or old accounts that have not been removed or disabled when they should have been.

There are several ways that no-longer-valid user accounts can lead to serious trouble:
  1. Former users may have (or develop) malicious intent. The most obvious way that a departed user's account can cause harm is if that user decides to try to login and use their ersatz account to wreak havoc. This happens more often than you'd expect, sometimes with tragic consequences. In the Sony Pictures hack, as well as the recent AshleyMadison hack, one commonly-cited theory is that former employees were involved.

  2. Former employees may have accounts with external cloud-based services that they use on behalf of your organization. With the proliferation of such services, it is essential to track the creation and use of such accounts to ensure that access to such accounts can be terminated when an individual leaves the organization or changes job responsibilities and no longer requires such access.

  3. Old accounts can be abused by an external intruder or a malicious insider. One common way that intrusions get detected is when a user notes the abuse of his/her own access privileges. For instance: "Why does the server say I'm already logged in? I've been on vacation for two weeks!" So the most advantageous accounts for an intruder to user are those that nobody uses anymore, and attackers will seek out such accounts, or even reactivate old accounts to use in order to act with less risk of detection.

http://www.csoonline.com/article/2930712/access-control/do-departed-employees-haunt-your-networks.html

http://www.scmagazine.com/disgruntled-former-employee-pleads-guitly-to-power-supplies-co-hack/article/402473/

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