Active Directory (AD)

Active Directory is Microsoft's directory service that allows administrators to assign policies, deploy software, and apply updates for an entire organization. AD also allows users to store data in a central location, where it is backed up.

Benefits of Active Directory

Active Directory is a state-wide authentication directory that supports enterprise systems, provides contact information and scheduling integration, along with providing mechanisms for centralized desktop management. There are multiple Active Directory (AD) environments in use across the University of Tennessee campuses and institutes. The purpose of the Active Directory Project is to migrate all of these environments into a single AD forest, which will provide the following benefits:

1. Single user name and password - NetID
2. Password synced between AD and LDAP Directory Services
3. Reduce overhead through standardization
4. Improve services through centralized management capabilities
5. Provide foundation for the following AD related services: a)SharePoint    b)Exchange
6. Improve workstation security
7. Central storage provided for individuals and departments
8. Backup and restoration services for central storage
9. Server storage space for user documents
10. Backed up data on Home and Departmental drives
11. Lower departmental cost because infrastructure is managed and maintained by OIT

Q: - What is Authentication Header and how it provides the protection to IP header?

Basically Authentication Header protects IP header and provides the complete authenticity to the IP packets.AH may work in two ways: transport mode and tunnel mode.

In tunnel mode; Authentication Header protects the IP header using two IP header layers inner and outer. The inner IP header is used to contain the source and destination addresses, and the outer IP header is used to contain the security gateway information.

Q: - if We have to generate a hash function then what characteristics are needed in a secure hash function?.

• A secure hash function should have the following characteristics:
• The output generated by a hash function should be of a fixed length. 
• It should be very easy to find out a hash function for a given message. 
• If a hash value is given of a message than it is almost impossible to get that message. 
• The two different messages should not have the same hash value; it is against the hash function property. 

For authentication: One can encrypt the hash (MD4/SHA) of the data with a private key. This is known as a digital signature.
To prevent DoS attacks firewall can be configured as a relay; in this approach the firewall responds on behalf of the internal host. During the attack, the firewall responds to the SYN sent by the attacker; since the ACK never arrives, the firewall terminates the connection. By Keeping protocols and Antivirus software up-to-date, we can prevent being a victim of DoS. A regular scanning of the machine is also necessary in order to detect any anomalous behavior.

Q: - What are the differences among encoding, encryption and hashing?

Encoding: Basically encoding is used to protect the integrity of data as it crosses through a communication network to keep its original message upon arriving. It is primarily an insecure function because it is easily reversible.

Encryption: Encryption is basically designed for confidentiality and data integrity and reversible only if you have the appropriate key.

Hashing: With hashing the operation is one-way i.e. non-reversible. It takes an input (or , message ) and returns a fixed-size string, which is called the hash value.

Q: - What is Data encryption?

Data encryption ensures data safety and very important for confidential or critical data. It protects data from being read, altered or forged while transmission.

Q: - What is Digital Signatures ?

A digital signature is an attachment to an electronic message used for security purpose. It is used to verify the authenticity of the sender.

Q: - How do you use RSA for both authentication and secrecy?

RSA is a public key encryption algorithm. The RSA algorithms are based on the mathematical part that it is easy to find and multiply large prime numbers together, but it is extremely difficult to factor their product.

Q: - If you are a victim of Denial of Service (Dos) then what you do?

The function of a denial of service attack is to flood its target machine with too much traffic and prevents it from being accessible to any other requests or providing services.

Error in Excel 2007 : "There was a problem sending the command to the program"

If you have ever tried to open an excel document and received the error that says "There was a problem sending the command to the program", you can fix it by doing the following:

1. Open Excel 2007

2. Open the Menu on the top left

3. Click the "Excel Options" button

4. Click the advanced tab on the left of the options screen

5. Under the general options un-check the box "Ignore other application that use Dynamic Data Exchange (DDE)"

How to Bridge an Internet Connection

Wireless has taken a huge leap in usage thanks to a huge improvement in its usability over the years. That's good for many portable devices such as laptops, smart phones, etc. But for people using desktops, a wireless adapter may not be included. Or, you may want to have a more stable wireless connection than the one you currently have.

Bridging an internet connection refers to making connections between different ports that will be used by your computer, such as Ethernet and wireless. Shown in this article are simple steps that you can use to create your own bridged connection.

1 ) Make sure the relevant machines and crossover cable are working. 
To see if the cable is working, plug it into both machines. If the port lights up, then you know that it works. If it does not light up, the cord is not in working order.

2) Get started. 
On both machines, go the the start menu, open the control panel and go to "Network and Internet". The Local Area Connection (LAN) should show up with no internet access in the window.

3) Create the bridge on the host machine.
Go to "Change adapter settings" on the left pane on the host machine. Two or more connections should show up. Highlight both Local Area Connection and Wireless Network Connection. Right click one of the icons you highlighted and an options menu should come up with only "Bridge Connection". Click it and it should take a second to set up the connection.


The bridge is already working? Some machine cards will automatically assign the needed network information for you. If it does, an icon on the client machine's task bar will show up with a monitor and a fork like plug showing beside it. If the icon has a caution sign, it means that the information needs to be assigned manually.

4) Do error checking. 

A new icon should show up in the window called "Network Bridge" and it should display the name of the wireless network you are connected to below "Network Bridge". If not, repeat step 3 to remove the bridge and restart the process.

5) Access the command line. 

Still on the host machine, open the start menu and in the search bar type "CMD". Open Notepad and be prepared to write down your network information.

6) Get the machine's network information. 

In the CMD window, type "ipconfig /all". A large list of information should show up. Scroll to the top and look for "Ethernet adapter Network Bridge:", copy the IPv4 Address, Subnet Mask, Default Gateway, and the DNS Servers


7) Perform a client machine setup. 
On the client machine, click on "Local Area Connection". A window should pop up called "Local Area Connection Status"; select Properties, and in that window double click "Internet Protocol Version 4 (TCP/IPv4)".

8) Enter the IP information. 

To enter the network information, select "Use the following IP Address". Now the three bars should be lit up. In the IP address row, enter the IPv4  address of the host machine, and  in the last section of numbers increase it by  1.

Example: 192.168.1.179 becomes 192.168.1.180. The Subnet Mask is the same as what was copied as with the Default Gateway.

9) Check the DNS servers. 

The DNS servers will also be changed to what was copied down from the host machine's network information. For the first row, enter the information as it was from the Host, and in the second row put in the same number but increase the last number by 1.

Example: 192.168.1.1 and 192.168.1.2.

10) Finalize the connection.  

Click the box about Validating Settings upon exit and click OK. It will take a second to validate but the connection should start working a few seconds after clicking OK. Your new connection should be working now.

Error: Windows Explorer has stopped working

1) Run System File Checker (CFS) to check yours Files

Use System File Checker to scan your PC for missing or corrupt files. To do this, follow these steps:

1. Click Start, and then type cmd in the Search box.2. In the results area, right-click cmd.exe, and then click Run as administrator. You may be prompted to type the password for an administrator account.
3. Click Continue if you are the administrator or type the administrator password and then, click Continue.
4. At the command prompt, type Sfc /scannow and then press ENTER.

2) Test your system's RAM memory

Sometimes Faulty RAM (Random-Access Memory) can cause intermittent problems within Windows. Use the Windows Memory Diagnostics Tool by clicking Start, type Memory Diagnostics and select the result in the list. When the Windows Memory Diagnostics Tool window appears, choose Restart now and check for problems (recommended).

3) Test for picture files that may contain Corruption

Corrupt images can sometimes issues with Windows Explorer. If Windows Explorer stops working while working with pictures or browsing folders that contain pictures, there may be corruption is one or more picture files. To test for this issue, follow the steps below:

1. Click Start and click Computer
2. Click Organize and select Folder and search options from the dropdown

3. On the Folder Options window, click the View tab
4. Place a check in the option to Always show Icons, never thumbnail
5. Remove the check for the option to Display file icon on thumbnails
6. Click OK to close the Folder Options window

Now, go to any folders that contain Pictures or Videos and see if you can reproduce the issue. If Windows Explorer does stop working, the folder that you were viewing possibly contains one or more pictures files that are corrupt or contain corrupted thumbnail data.

Note: After adjusting the options to Display file icon on thumbnails, and Always show Icons, never thumbnail, files no longer display thumbnails so pictures and other files will display as the default icon for their file types. If you can reproduce the error with these options set, the issue is not with pictures or videos and you should return the Folder options to their original settings.

Check the details of the error to see which application caused Windows Explorer to stop working. To do this, follow these steps:

1. Click Start and type Action Center in the Search area and click Action Center from the returned list
2. In the Action Center window, click Maintenance, click View reliability history 

     and then click View all  problem reportsfrom the bottom of the Reliability Monitor window
3. Scroll down to the list of Windows Explorer items
4. Double-click on Stopped working to view technical details and then make a note of the technical details.