What is an access control list (ACL)?

A list of rules that indicate which individuals or systems are permitted access to a particular object or system resource and which are not is called an access control list, or ACL. Access control lists can also be installed in switches or routers, where they manage the traffic that is allowed to enter the network environment and act as filters.

Every system resource has a security attribute that describes the resource's access control list. An entry on the list represents each and every user who has access to the system. The characteristics most commonly associated with access control lists (ACLs) for file systems include the capacity to read a file or all of the files in a directory, the capacity to make changes to the file or files, and the capability to execute the file if it is an executable file or program. Additionally, operating systems (OSes) like Windows and Linux, as well as network interfaces, integrate access control lists (ACLs). On a computer network, access control lists are used to either allow or prohibit specific types of traffic from entering the network. They routinely censor communications based on their origin and destination.

What are access control lists used for?

Access control lists are used to manage the permissions that are given to a computer system or computer network. They can be used to filter traffic entering and leaving a particular device. These devices could be endpoint devices that users can access directly over the network or network devices that serve as network gateways.

Depending on the responsibilities they play, different users on a computer system are given different levels of rights. For example, someone who is logged in as the network administrator may be able to read, write, and modify a sensitive file or other available resource. In contrast, someone who is logged in as a visitor may just have read permissions.

Access control lists can help organize traffic to increase network efficiency and give administrators fine-grained control over users on their computer systems and networks. Additionally, by blocking malicious traffic, access control lists (ACLs) can be used to improve network security.

How do ACLs work?

Each access control list (ACL) contains one or more access control entries (ACEs) that contain the name of a user or group of users. The user could also be a role name, such as a programmer or tester. Each of these users, groups, or roles' access privileges is specified by an access mask, which is a string of bits. The access mask shows these access rights. The creation of an object's access control list is frequently the responsibility of a system administrator or the object's owner.

ACCESS CONTROL LIST (ACL)

Types of access control lists

There are two basic types of ACLs:

File system ACLs: ACLs are used to manage access to directories and files within a file system. After the system has been accessed, they provide operating systems with the instructions that define user access rights for the system, as well as the privileges that are granted to users.
Networking ACLs: Administrative control lists (ACLs) in networking are used to govern network access by supplying instructions to network switches and routers. These instructions identify the types of traffic that are permitted to interface with the network. Once a user is within the network, these access control lists (ACLs) also specify user permissions. The rules for the networking access control list are predefined by the network administrator. Thus, they perform a function that is comparable to that of a firewall.

ACLs can also be categorized by the way they identify traffic:

● Standard ACLs: Using source IP addresses, standard access control lists (ACLs) either prohibit or allow a full protocol suite.

● Extended ACLs: Instead of merely blocking or allowing network traffic based on the source address alone, extended access control lists (ACLs) prohibit or allow traffic based on a more distinct collection of attributes that includes source and destination IP addresses as well as port numbers.

Benefits of using an ACL

There are several benefits of using an ACL, including the following:

● Simplified user identification. An access control list can make it easier to identify a person. Access control lists, or ACLs, guarantee that a system can only be accessed by authorized users and traffic.

● Performance. Access control lists (ACLs) provide performance advantages over other technologies that provide the same function. Access control lists do not negatively affect routing device performance because they are directly configured on the forwarding hardware of the routing device. Consider this in contrast to a stateful inspection firewall, which is an independent piece of software that may result in a decline in performance. Networks can function more efficiently by managing their traffic.

● Control. Using access control lists (ACLs), administrators can have more granular control over the permissions granted to users and traffic on a network at a variety of different points throughout the network. They can help regulate traffic flowing between internal networks and access to network endpoints.

Where can you place an access control list?

It is highly feasible to install ACLs or access control lists on practically any security or routing device, and it can possibly be beneficial to have several ACLs installed in numerous locations of the network configuration.

Access control lists (ACLs) are a great option for network endpoints like servers or apps that require high performance and speed in addition to security.

Administrators may choose to place an access control list at different network connections, depending on the network's architecture. Access control lists (ACLs) are often implemented on edge routers because they are situated at the edge of a network. As a result, traffic can be filtered by the Access Control List (ACL) before it is sent to the rest of the network.

Edge routers with access control lists (ACLs) installed can establish a demilitarized zone (DMZ) between the public internet and the rest of the network. A buffer zone with an outward-facing router that provides extensive defense against all external networks is called a demilitarized zone (DMZ). It also features an internal router that separates the demilitarized zone from the secured network.

DMZs may contain a variety of network resources, including application servers, web servers, domain name servers, and virtual private networks. The devices behind the routing device and the kind of users who need access to those devices can affect how the access control list (ACL) is configured.

Components of an access control list

The numerous components that make up an entry in the Access Control List (ACL) show how the ACL manages different types of traffic. Examples of parts that are frequently seen in ACL assemblies include the following:

● Sequence number. The sequence number can be used to identify the object contained in the ACL entry.

● ACL name. This uses a name instead of a number to identify an Access Control List (ACL). Some ACLs allow both letters and numbers.

● Comments. Certain access control lists (ACLs) allow users to add comments that elaborate on the ACL item.

● Network protocol. Network protocols like Internet Protocol (IP), Internet Control Message Protocol (ICP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), or NetBIOS, for instance, allow or prohibit transmission.

● Source and destination. This identifies a range of IP addresses and a specific IP address that can be prohibited or permitted in compliance with Classless Inter-Domain Routing.

● Log. A log of the objects that the ACL recognizes is kept by certain of the ACL devices.

The capacity to identify traffic based on specific IP packet header data, such as Differentiated Services Code Point, Type of Service, or IP precedence, is made possible by more intricate Access Control List (ACL) entries.

How to implement an ACL?

Network administrators must have a thorough awareness of the various types of traffic that enter and leave the network, as well as the resources they are trying to protect, in order to create an access control list (ACL). Information technology assets should be arranged and managed by administrators in a hierarchical structure, with different categories and user privileges.

Deploying a standard access control list (ACL) in close proximity to the target it is trying to protect is a conventional procedure. Extended access control lists are usually implemented near the source. Extended access control lists (ACLs) can be configured by using access list names instead of access list numbers.

An illustration of the basic syntax used to create a standard numbered access control list on a Cisco router is provided below:

Router (config)# access-list (1300-1999) (permit | deny) source-addr (source-wildcard)

The various parts mean the following:

● (1300-1999) specifies the ACL IP number range. This names the ACL and defines the type of ACL. 1300-1999 makes this a standard ACL.

● (permit | deny) specifies the packet to permit or reject.

● Source-addr specifies the source IP address.

● Source-wildcard specifies the wildcard mask.

By employing a wildcard mask, a router may identify which portions of an IP address are reachable by a network device. It can then examine those portions to see if they match the access list.

Users can generate the access control list by entering the previously supplied configuration code into the command line. Additionally, cloud platforms from suppliers like IBM and Oracle frequently give customers the option to create an access control list on their login page.

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Understands The Access Control List in Networking - Craw Security

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