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Critical 15 Year-old Linux Security Hole (Ghost) Revealed

Posted in Linux System and Network Services

Critical 15 Year-old Linux Security Hole (Ghost) Revealed - 5.0 out of 5 based on 1 vote

linux-ghost-security-gnu-lib-vulnerability-1Security researchers at qualys.com yesterday released information on a critical 15 year-old Linux security hole which affects millions of Linux systems dated back to the year 2000.  The newly published security hole – code named ‘Ghost’  was revealed yesterday by Qualy’s security group on openwall.com. Readers interested can read through the summary and analysis here.

The security hole was found in the __nss_hostname_digits_dots() function of the GNU C Library (glibc).

The function is used on almost all networked Linux computers when the computer tries to access another networked computer either by using the /etc/hosts files or, more commonly, by resolving a domain name with Domain Name System (DNS)

As noted by the security team, the bug is reachable both locally and remotely via the gethostbyname*() functions, making it possible remotely exploit it by triggering a buffer overflow by using an invalid hostname argument to an application that performs DNS resolution.

The security hole exists in any Linux system that was built with glibc-2.2 which was released in November 10th, 2000. Qualy mentioned that the bug was patched on May 21st, 2013 in releases glibc-2.17 and glibc-2.18.

Linux systems that are considered vulnerable to the attack include RedHat Enterprise Linux 5, 6 and 7, CentOS 6 and 7Ubuntu 12.04 and Debian 7 (Wheezy).

Debian has is already patching its core systems (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=776391) while Ubuntu has already patched its 12.04 and 10.04 distributions (http://www.ubuntu.com/usn/usn-2485-1/). CentOS patches are also on their way.

How To Change & Configure An IP Address or Set to DHCP, Using The Command Prompt In Windows 7

Posted in Windows XP, Windows Vista, Windows 7

How To Change & Configure An IP Address or Set to DHCP, Using The Command Prompt In Windows 7 - 5.0 out of 5 based on 1 vote

Not many users are aware that Windows 7 provides more than one way to configure a workstation’s network adaptor IP address or force it to obtain an IP address from a DHCP server. While the most popular method is configuring the properties of your network adaptor via the Network and Sharing Center, the less popular and unknown way for most users is using the netsh Command Prompt. In this tutorial, we show you how to use the Command Prompt netsh command to quickly and easily configure your IP address or set it to DHCP.  Competent users can also create simple batch files (.bat) for each network (e.g home, work etc) so they can execute them to quickly make the IP address, Gateway IP and DNS changes.

In order to successfully change the IP address via Command Prompt, Windows 7 requires the user to have administrative rights. This means even if you are not the administrator, you must know the administrative password, since you will be required to use the administrative command prompt.

 

Opening The Administrative Command Prompt on Windows 7

To open the administrative command prompt in Windows 7, first click on the Start icon. In the search dialog box that appears, type cmd and right-click on the cmd search result displayed. On the menu that Windows brings up, click on the Run as administrator option as shown in the below screenshot:

windows-7-change-ip-address-via-cmd-prompt-1Figure 1. Running CMD as Administrator

Depending on your User Account Control Settings (UAC), Windows may ask for confirmation. If this happens, simply click on Yes and Windows will present the CLI prompt running in elevated administrator privileged mode:

How to View Hidden Files and Folders In Windows 8 & 8.1

Posted in Windows 8 & Windows 8.1

How to View Hidden Files and Folders In Windows 8 & 8.1 - 5.0 out of 5 based on 1 vote

windows-8-how-to-show-hidden-folders-files-1aWindows 8 & 8.1 hides two types of files so that normally, you do not see them while exploring your computer. The first type is the files or folders with their 'H' attribute set to make them hidden. The other type is Windows System files. The reason behind hiding these files is that users could inadvertently tamper with them or even delete those causing the operations of Windows 8/8.1 to fail. This article explains how you can configure Windows 8 or 8.1 to show all hidden files and folders, plus show Windows system files.

You can change the behavior of your Windows 8/8.1 computer to show hidden files by changing the settings in the Folder Options screen. There are two primary ways you can reach the Folder Options screen. Both are analysed below:

Windows 7 users can also refer to our How to View Hidden Files and Folders In Windows 7 article

Method 1: Making Hidden and System Files Visible from Windows Explorer

Begin from the Start Screen by closing down all open applications.

Step 1: Tap/click on the Desktop tile to bring up the Windows Desktop.

Step 2: Tap/click on the Files Explorer icon in the Panel at the bottom left hand side of your Desktop:

How to View Hidden Files & Folders in Windows 7

Posted in Windows XP, Windows Vista, Windows 7

How to View Hidden Files & Folders in Windows 7 - 5.0 out of 5 based on 4 votes

windows-7-showing-hidden-files-1This article shows you how to see hiddeen files and folders in Windows 7. Windows 7 hides important system files so that normally, you do not see them while exploring your computer.

The reason behind hiding these files is that users could inadvertently tamper with them or even delete those causing Windows 7 operations to falter. However, malicious software programs take advantage of this feature to create hidden files or folders and cause disruptions in the computer's operations without the user being able to detect them.

Therefore, being able to see hidden files or folders has its advantages and helps in repairing damages caused by unwanted hidden files. You can change the behavior of your Windows 7 computer to show hidden files by changing the settings in the Folder Options screen. There are two primary ways you can reach the Folder Options screen. Start by closing down all open applications.

Windows 8 and 8.1 users can also refer to our How to View Hidden Files and Folders In Windows 8 & 8.1 article

Method 1: Reaching the Folder Options screen from Windows Explorer

Click on the Windows Explorer icon in the TaskBar at the bottom left hand side of your Desktop:

windows-7-showing-hidden-files-2Figure 1. Icons in the Windows Panel

When the Explorer window opens, you have to click on the Organize button to display a drop down menu:

How and Why You Should Verify IOS Images On Cisco Routers & Catalyst Switches. Identify Corrupt & Tampered Images using SHA2 or MD5 Verification

Posted in Cisco Routers - Configuring Cisco Routers

How and Why You Should Verify IOS Images On Cisco Routers & Catalyst Switches. Identify Corrupt & Tampered Images using SHA2 or MD5 Verification - 4.5 out of 5 based on 4 votes

cisco-router-switch-ios-image-verification-sha2-md5-1Chances are we’ve all needed to upgrade our Cisco’s device IOS software at some point. While upgrading the IOS software on a Cisco device is considered to be a fairly simple process, it can turn out to be a very stressful and destructive process if something goes wrong, especially if the upgrade is being performed on a remote Cisco device. Uploading a corrupt IOS image or having it become corrupt during the upload process is a common problem Cisco engineers encounter.

If a corrupted IOS image is not identified before the reload/reboot of the device, it’s most likely the device will not boot again unless a special recovery procedure is followed. A corrupt IOS image translates to network downtime, service disruption and possibly financial loss for the company.

Therefore verifying an IOS image that has been uploaded to a Cisco device is a very important step, regardless how experienced one might be.  Unfortunately most network engineers skip or are totally unaware of the image verification process and the trouble it can help them avoid.

Here are a few reasons why Cisco IOS image verification should become a mandatory step during any upgrade:

  • It helps ensure the IOS image is not corrupt
  • It avoids unnecessary surprises after a router/switch reload - especially when it’s at a remote location!
  • It verifies the integrity of the software
  • Reduces the risk of malicious code being installed on the Cisco IOS device
  • TFTP, the method often used to upload files, cannot guarantee error-free transfers
  • Helps maintain your professional image and reliability :)


Using the SHA2/MD5 File Verification Feature

The MD5 File Validation feature was added in Cisco IOS Software Releases 12.2(4)T and 12.0(22)S onwards. This feature allows the administrator to calculate the MD5 hash of a Cisco IOS software image previously loaded on a device's flash.

Newer IOS images and ISR routers now make use of the SHA2 algorithm, rather than the older MD5, however we can optionally verify the image using MD5.

Cisco publishes the MD5 hash value (Checksum) for every software image in their download area. This enables the network engineer to easily check and compare the calculated MD5 hash value against Cisco’s site and identify any signs of tampering.

Note: The commands might slightly differ depending on the device you are working on (Cisco Router or Catalyst Switch) and the running version of the IOS software.

Below is a Cisco 2921 router that has just had an IOS image uploaded (c2900-universalk9-mz.SPA.152-4.M6a.bin):

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