Home > Articles > Security > General Security and Privacy

"Open Sesame" or Not? Use the Right Access Controls

📄 Contents

  1. Use the Right Access Controls on Network Servers
  2. Use the Right Access Controls On Public Web Servers
What's the secret to configuring network servers securely? Use the right access controls on both general purpose servers and public Web servers.
Like this article? We recommend

In our previous article, Stick to the Essentials,we made the point that more than 99 percent of intrusions result from the exploitation of known vulnerabilities or configuration errors, even though countermeasures and solutions are available. This excerpt from The CERT® Guide to System and Network Security Practices (Addison-Wesley, 2001, ISBN: 020173723X), and the CERT security improvement modules Securing Network Servers and Securing Public Web Servers advises administrators to configure network servers securely by applying two essential practices: Use the right access controls on general purpose servers, and use the right access controls on public Web servers. The second practice assumes that the guidelines described in the first have been followed.

Vendors sell systems configured so their customers will be eager to buy. Often, systems are general-purpose, that is, fully featured with most of the software enabled for ease of use. They are meant to satisfy everyone's needs and, perhaps, some they didn't realize they had. Such systems frequently contain

  • services that are unneeded and often insecurely configured

  • little to no protection against intruders accessing data objects such as files and directories

  • ease-of-use features often provided at the expense of security

  • vulnerabilities that intruders can use to break into systems

Given a user's or user group's role and access authority, administrators are responsible for implementing user privileges to access any data object on any network server. Access controls need to be configured to allow users to do their jobs while, at the same time, protecting the organization's critical data from breaches in confidentiality, integrity, and availability.

Use the Right Access Controls On Network Servers

Many operating systems provide the capability to specify access privileges individually for files, directories, devices, and other data or code objects. We recommend configuring the settings on files and other objects to take advantage of this capability and protect information in accordance with the organization's security policy.

The biggest challenge for administrators setting up access controls on data items in an operating system's file system is knowing what level of access is appropriate and correct. They must determine which identities need what type of access to properly use the data items in question.

Why This Is Important

Carefully setting access controls reduces the risk of both intentional and unintentional security breaches. For example, denying read access helps to protect confidentiality of information, while denying unnecessary write (modify) access can help maintain its integrity. Limiting the execution privilege of most system-related tools to authorized system administrators can prevent general users from making configuration changes that could reduce security. This restriction can also make it harder for intruders to use those tools to attack the system or other systems on the network.

How to Do It

Some operating systems provide a number of file systems, each with different access control capabilities. It is important to choose the file system that best meets requirements for file access control. This decision may affect the low-level formatting of storage devices, so it should be made early in the process of configuring the operating system.

Implement access controls during initial installation and configuration of the operating system. Carefully monitor and maintain them thereafter.

Identify the Level of Protection Needed

Restrict access to data based on groups, not individuals. For example, instead of giving read-only access to the Master Auto Parts File to the identities Manny, Moe, and Jack, the administrator first creates a group named Master_Auto_Parts_File_Read_Only, and places the identities Manny, Moe, and Jack into this group. The access control lists associated with the Master Auto Parts File are changed to grant read-only access to the group Master_Auto_Parts_File_Read_Only. If that triumvirate ever changes, only the group definition needs to change; the file need never change, even if no one is a member of the Master_Auto_Parts_File_Read_Only group. Plus, the group's name helps to document the access granted to those who are members. Use groups even if they contain only one member.

One method that can be used to identify needed protection is to construct a matrix with categories of files and objects on one axis and groups of users (defined by roles and access authority) on the other. Then, record in the matrix the kinds of access privileges allowed for that class of objects and that class of users. The privileges are based on the security requirements (such as confidentiality, integrity, and availability) of the various classes of resources.

For example, file categories may include administrative information (user names, passwords, privileges, and so on), applications, development tools, operating system files, and user data files. The latter may be further subdivided into categories such as customer accounts, inventory records, research data, and management reports. User groups may include system administrators, network service daemons, and users from various departments.

Privilege identification may result in the need to split some rows and columns. This happens, for example, upon discovering that a single group of users is really two groups because their needs to access a particular resource is not uniform.

Consider distinguishing local access privileges from network access privileges for a class of files.

Application programs may request and be granted increased access privileges for some of their operations—a change that is not obvious to the users of that application, and may not be desired. Therefore, it is important to take great care in assigning privileges to users and groups.

Configure the operating system to recognize the needed user groups and then assign individual users (including network service daemons) to the appropriate groups.

Configure Access Controls

Configure access controls for all protected files, directories, devices, and other objects using the matrix created in the first step as a guide. Every change or decision not to change each object's permission should be documented, along with the rationale.

The least privilege principle should be used when deciding how to implement access control lists. In other words, grant permissions to those user groups that need to have access and then allow those groups only the access levels they absolutely require. For example, if a group needs Read access to a folder, resist the temptation to give the group Full control, and grant only Read access.

Consider the following:

  • Disable write/modify access permissions for all executable and binary files.

  • Restrict access of operating system source files, configuration files, and their directories to authorized administrators.

  • For UNIX systems, there should be no world-writable files unless application programs specifically require them. For Windows systems, there should be no permissions set so that "the Everyone group has Modify permissions to files."

  • For UNIX systems, if possible, mount file systems as read only and nosuid to preclude unauthorized changes to files and programs.

  • Assign an access permission of immutable to all kernel files if assigning such a permission is supported by the operating system (such as Linux and FreeBSD).

  • Establish all log files as "append only" if that option is available.

  • Aim to preclude users from installing, removing, or editing scripts without administrative review. We realize that this restriction is difficult to enforce. Refer to the practices Consider Security Implications for Programs, Scripts, and Plug-ins and Configure the Web Server to Minimize the Functionality of Programs, Scripts, and Plug-ins in the references noted at the beginning of this article.

Pay attention to access control inheritance when defining categories of files and user groups. Ensure that the operating system is configured so that newly created files and directories inherit appropriate access controls, and so that access controls propagate down the directory hierarchies as intended when assigned.

Many of an administrator's security directives can be overridden on a per-directory basis. The convenience of being able to make local exceptions to global policy is offset by the threat of a security hole being introduced in a distant subdirectory, which could be taken over by a hostile user. Administrators should disable a subdirectory's capability to override top-level security directives unless that override is required.

Install and Configure File Encryption Capabilities for Sensitive Data

Some operating systems provide optional file encryption; there are also third-party file encryption packages available, which may be useful if the operating system's access controls are insufficient to maintain the confidentiality of file contents. This situation can occur if the operating system provides few or no access control features, or when the relationships among categories of files and categories of users are so complex that it would be difficult to administer the security policy using only access controls.

The security provided by strong access controls is further enhanced by the use of encryption. However, when using encryption, an administrator must still dispose of unencrypted versions of the data that existed prior to encryption being performed, remain after decrypting, and are used in the encryption process. Encryption adds complexity, so weigh the need for it against the cost of using it.

NOTE

Note that this recommendation pertains only to the encryption of files stored on the server itself. Encryption of information for transmission over a network is a separate issue that is not within the scope of this practice.

Policy Considerations

An organization's security policy for networked systems should specify the following:

  • Access privileges and controls for the information that will be stored on servers

  • Ways to access the files that have been encrypted with a user key. This information is very important when that user no longer works for the organization.

  • Access privileges and controls for administrators, such as

  • the authority and conditions for reading other users' e-mail

  • access to protected programs or files

  • disruption of service under specific conditions

  • a ban on sharing accounts

  • a ban on the unauthorized creation of user accounts

  • the authority and conditions for using vulnerability testing tools

  • the authority and conditions for using password cracking tools

The AusCERT Unix Checklist recommends permission settings as well as tasks for administrators to complete when adjusting access control lists (ACLs) on a Unix- or Linux-based system.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020