Network Security access lists standards and extended

Network security Reconnaissance attack

A reconnaissance attack occurs when an adversary tries to learn information about your network
Reconnaissance is the unauthorized discovery and mapping of systems, services, or vulnerabilities.
Reconnaissance is also known as information gathering and, in most cases, precedes an actual access or DoS attack. First, the malicious intruder typically conducts a ping sweep of the target network to determine which IP addresses are alive. Then the intruder determines which services or ports are active on the live IP addresses. From this information, the intruder queries the ports to determine the type and version of the application and operating system running on the target host.

Reconnaissance is somewhat analogous to a thief investigating a neighborhood for vulnerable homes, such as an unoccupied residence or a house with an easy-to-open door or window. In many cases, intruders look for vulnerable services that they can exploit later when less likelihood that anyone is looking exists.

Access Attacks

An access attack occurs when someone tries to gain unauthorized access to a component, tries to gain unauthorized access to information on a component, or increases their privileges on a network component. Access attacks exploit known vulnerabilities in authentication services, FTP services, and web services to gain entry to web accounts, confidential databases, and other sensitive information.

DoS Attacks

DoS attacks involve an adversary reducing the level of operation or service, preventing access to, or completely crashing a network component or service.

Password Attacks

A password attack usually refers to repeated attempts to identify a user account, password, or both. These repeated attempts are called brute-force attacks. Password attacks are implemented using other methods, too, including Trojan horse programs, IP spoofing, and packet sniffers.

Password attack threat-mitigation methods

A security risk lies in the fact that passwords are stored as plaintext. You need to encrypt passwords to overcome risks. On most systems, passwords are processed through an encryption algorithm that generates a one-way hash on passwords. You cannot reverse a one-way hash back to its original text. Most systems do not decrypt the stored password during authentication; they store the one-way hash. During the login process, you supply an account and password, and the password encryption algorithm generates a one-way hash. The algorithm compares this hash to the hash stored on the system. If the hashes are the same, the algorithm assumes that the user supplied the proper password.

Remember that passing the password through an algorithm results in a password hash. The hash is not the encrypted password, but rather a result of the algorithm. The strength of the hash is that the hash value can be recreated only with the original user and password information and that retrieving the original information from the hash is impossible. This strength makes hashes perfect for encoding passwords for storage. In granting authorization, the hashes, rather than the plain password, are calculated and compared.

Password attack threat-mitigation methods include these guidelines:

  • Do not allow users to have the same password on multiple systems. Most users have the same password for each system they access, as well as for their personal systems.
  • Disable accounts after a specific number of unsuccessful logins. This practice helps to prevent continuous password attempts.
  • Do not use plaintext passwords. Use either a one-time password (OTP) or an encrypted password.
  • Use strong passwords. Strong passwords are at least eight characters long and contain uppercase letters, lowercase letters, numbers, and special characters. Many systems now provide strong password support and can restrict users to strong passwords only.

The standard authentication protocols used by various network services, such as RAS and VPN, for authentication include the following:

Password Authentication Protocol

Password Authentication Protocol (PAP) The Password Authentication Protocol sends the user’s username and password in plain text. It is very insecure because someone can analyze and interpret the logon traffic. This is the authentication protocol used by the basic authentication method mentioned previously.

Challenge Handshake Authentication Protocol

Challenge Handshake Authentication Protocol (CHAP) With the Challenge Handshake Authentication Protocol, the server sends a client a challenge (a key), which is combined with the user’s password. Both the user’s password and the challenge are run through the MD5 hashing algorithm (a formula), which generates a hash value, or mathematical answer, and that hash value is sent to the server for authentication. The server uses the same key to create a hash value with the password stored on the server and then compares the resulting value with the hash value sent by the client. If the two hash values are the same, the client has supplied the correct password. The benefit is that the user’s credentials have not been passed on the wire at all.

Microsoft Challenge Handshake Authentication Protocol MS-CHAP

Microsoft Challenge Handshake Authentication Protocol MS-CHAP uses the Microsoft Point-to-Point Encryption (MPPE) protocol along with MS-CHAP to encrypt all traffic from the client to the server. MS-CHAP is a distinction of the CHAP authentication protocol and uses MD4 as the hashing algorithm versus MD5 used by CHAP.

MS-CHAPv2

MS-CHAPv2 With MS-CHAP version 2 the authentication method has been extended to authenticate both the client and the server. MS-CHAPv2 also uses stronger encryption keys than CHAP and MS-CHAP.

Extensible Authentication Protocol (EAP)

Extensible Authentication Protocol (EAP) The Extensible Authentication Protocol allows for multiple logon methods such as smartcard logon, certificates, Kerberos, and public-key authentication. EAP is also frequently used with RADIUS, which is a central authentication service that can be used by RAS, wireless, or VPN solutions.

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