DNS Changer Malware- its effects and how to secure your computer from this

DNSChanger Malware has been infecting computers from November last year.

The roughly half a million devices are still infected with DNSChanger.

Infected machines had their Domain Name System settings altered so websites would redirect to servers controlled by the criminals. The scammers reportedly earned millions in affiliate and referral fees by diverting users through those sites.

Computers affected with this Trojan will not be able to access Internet after 9th July.

If infected machines are not fixed by then, their Internet connections will go dark.

On Google, infected computers will see a warning atop their screen when completing a search (see below). 

  

Read more about this Malware and how to check whether your computer has been infected by this here in FBI’s Publication

http://www.fbi.gov/news/stories/2011/november/malware_110911/DNS-changer-malware.pdf

Symantec Security "best practices" for system admins

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":
• Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
• Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
• Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
• Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
• If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
• If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.

Principles of Software Security

Principles of Software Security

Security is a major concern for the Softwares we design.

There are a number of established security principles that apply to the process of software design. These accepted principles help us design secure applications.

Have a look on these Security Principals:

• Adopt the principle of least privilege. Processes that run script or execute code should run under a least privileged account to limit the potential damage that can be done if the process is compromised. If a malicious user manages to inject code into a server process, the privileges granted to that process determine to a large degree the types of operations the user is able to perform. Code that requires additional trust (and raised privileges) should be isolated within separate processes.

  
  

• Use defense in depth. Place check points within each of the layers and subsystems within your application. The check points are the gate-keepers that ensure that only authenticated and authorized users are able to access the next downstream layer.
  
  
• Don't trust user input. Applications should thoroughly validate all user input before performing operations with that input. The validation may include filtering out special characters. This preventive measure protects the application against accidental misuse or deliberate attacks by people who are attempting to inject malicious commands into the system. Common examples include SQL injection attacks, cross-site scripting attacks, and buffer overflow.
  
  
• Use secure defaults. A common practice among developers is to use reduced security settings, simply to make an application work. If your application demands features that force you to reduce or change default security settings, test the effects and understand the implications before making the change.
  
  
• Don't rely on security by obscurity. Trying to hide secrets by using misleading variable names or storing them in odd file locations does not provide security. In a game of hide-and-seek, it's better to use platform features or proven techniques for securing your data.
  
  For example, all of your files that contain data like xml files, can be put in App_Data folder in an ASP.net application to make them secure and inaccessible from attackers.
  
• Check at the gate. You don't always need to flow a user's security context to the back end for authorization checks. Often, in a distributed system, this is not the best choice. Checking the client at the gate refers to authorizing the user at the first point of authentication (for example, within the Web application on the Web server), and determining which resources and operations (potentially provided by downstream services) the user should be allowed to access.

  
  If you design solid authentication and authorization strategies at the gate, you can circumvent the need to delegate the original caller's security context all the way through to your application's data tier.

• Assume external systems are insecure. If you don't own it, don't assume security is taken care of for you.
  
  
• Reduce surface area. Avoid exposing information that is not required. By doing so, you are potentially opening doors that can lead to additional vulnerabilities. Also, handle errors gracefully; don't expose any more information than is required when returning an error message to the end user.
  
  
• Fail to a secure mode. If your application fails, make sure it does not leave sensitive data unprotected. Also, do not provide too much detail in error messages; meaning don't include details that could help an attacker exploit a vulnerability in your application. Write detailed error information to the Windows event log.
  
  
• Remember you are only as secure as your weakest link. Security is a concern across all of your application tiers.
  
  
• If you don't use it, disable it. You can remove potential points of attack by disabling modules and components that your application does not require. For example, if your application doesn't use output caching, then you should disable the ASP.NET output cache module. If a future security vulnerability is found in the module, your application is not threatened.
  
  

Key Terminology

• Authentication. Positively identifying the clients of your application; clients might include end-users, services, processes or computers.
  
  
• Authorization. Defining what authenticated clients are allowed to see and do within the application.
  
  
• Secure Communications. Ensuring that messages remain private and unaltered as they cross networks.
  
  
• Impersonation. This is the technique used by a server application to access resources on behalf of a client. The client's security context is used for access checks performed by the server.
  
  
• Delegation. An extended form of impersonation that allows a server process that is performing work on behalf of a client, to access resources on a remote computer. This capability is natively provided by Kerberos on Microsoft® Windows® 2000 and later operating systems. Conventional impersonation (for example, that provided by NTLM) allows only a single network hop. When NTLM impersonation is used, the one hop is used between the client and server computers, restricting the server to local resource access while impersonating.
  
  
• Security Context. Security context is a generic term used to refer to the collection of security settings that affect the security-related behavior of a process or thread. The attributes from a process' logon session and access token combine to form the security context of the process.
  
  
• Identity. Identity refers to a characteristic of a user or service that can uniquely identify it. For example, this is often a display name, which often takes the form authority/user name.

References:

http://msdn.microsoft.com/en-us/library/aa302381.aspx#secnetch01_whataregoals