Defensive Measures at Data Layer Basic to In-depth Home Computer Security Guide Page 22

Defensive Measures at Data Layer

This is the fourth and core layer of the defense in depth model. The defensive measures that have to be taken at this layer are:

§User must backup his important files

§Use encryption to ensure confidentiality of sensitive data

§File Checksum

§Password Policy

§Login Settings

§Audit Policy Settings

§Event Viewer

User must backup his Important Files

Taking backups of important files is one of the important safety measures to be taken. It’s like keeping a spare tyre in the car while driving. Imagine the situation when one of the car’s tyre punctures and when driver is about to change that, he come to know that he does not have a spare tyre with him? Or what happens if the computer system malfunctions or is destroyed by a successful attacker?

Backing up data is a task user should perform regardless of whether his system is secured or not. As far as security is concerned, this is the last line of defense. If someone gains access to the system and delete files, then user will need to restore them from backup.

Confused!!!- Which file to save and which not. Here is a help to discriminate between the two. Generally files are divided in two broad categories:

• Files which can be replaced: like basic operating system or application files.

• Files which can’t be replaced: like family pictures, letters, invoices and account records etc.

Although it is the best practice to backup the whole system, but the constraint is of space available on the backup media. User can backup data to an external or removable hard drive, a personal tape drive, Zip or Jazz drive, CDburner or a DVD-burner or bare minimum on to floppy. If user has a CD-writer (which may take more than one CD to take full backup) or DVD-writer he can conveniently take the full backup of his system. But if user does not have these two then he has to decide formerly about the files he wants to take backup and according to the space requirement he can select his backup media.

Every Operating System provides the feature to take backups on different media. Apart from that different applications are also available which can take the backups like the application which come with CD- writer or DVD-writer.

There is an in-built program that comes with Windows Operating System which is called as “Backup”. It is located at Start>Programs>Accessories>System Tools, and is quite easy to operate. User just has to select the files for backup and the destination where he want to store.

How and where should user store his backup media after he backup data to them? Well, user needs to store them in a safe place—remember that they contain files that are virtually irreplaceable if lost or damaged. If user does not have a secure storage area, it must not let this to prevent him from doing regular backups: any backup is better that no backup!

The definition of regularity depends on the comfort level of the user, i.e. how much work is one prepared to lose? A daily backup would be ideal but a weekly backup might be more viable.

Use encryption to ensure confidentiality of sensitive data

With the newer versions of Windows, i.e. Windows 2000 and XP, the user can use the Encrypting File System (EFS) to encrypt important data files. By using such encryption, an intruder who gets through the entire defense in depth layers and tries to access encrypted files or folders will be prevented from doing so. The intruder will receive an access denied message if he tries to open, copy, move, or rename an encrypted file or folder, unless the intruder has determined the UID and password of either the system administrator or the user who created the encrypted file.

Once a file or folder is encrypted, the user can work with the encrypted file or folder just as he would with any other file and folder since encryption is transparent to the user that encrypted the file. This means that the user does not have to decrypt the encrypted file before using it.

A file or a folder can be encrypted, subject to the following constraints, by using Explorer selecting the file/folder and clicking on the “Encrypt contents to secure data” attribute on the advanced features of the properties page:

• Can only encrypt files and folders on NTFS file system volumes.

• Compressed files or folders cannot be encrypted.

• System files cannot be encrypted.

If the user should ever lose their file encryption certificate and associated private key (through disk failure or any other reason), then data recovery is available through the person who is the designated recovery agent.

Of course if the use of EFS is not an option, then a knowledgeable user could use PGP for this sort of encryption. However, using PGP would not be transparent like using EFS. PGP Freeware is available for non-commercial use.

Apart form these; if the user is not using EFS or PGP, then he should use at least NTFS (NT File System), which gives file level user security. Windows 9x does not support NTFS file system, a user should have at least Windows NT or above to use NTFS.

File checksum

File Checksum is a utility that computes MD5 or SHA1 cryptographic hashes for files. The File Checksum utility can generate MD5 or SHA-1 hash values for files to compare the values against a known good value. It can compare hash values to make sure that the files have not been changed. It can also compute hashes of all critical files and save the values in an XML file database. It could be used to check the changes or compromise of the computer against the XML database to determine which files have been modified.

Users are advised to calculate checksum of all the system files and compare them regularly against the threat of Trojans or backdoors.

Password Policies

Importance of a password

·Password represents the identity of an individual for a system.

·This helps individuals protect personal information from being viewed by unauthorized users. Hence it is important to secure passwords.

·Passwords acts like a barrier between the user and his personal information.

BASIC THINGS TO REMEMBER WHILE SETTING A PASSWORD

·Use at least 8 characters or more to create a password. More number of characters we use, more secure is our password.

·Use various combinations of characters while creating a password. For example, create a password consisting of a combination of lower case, uppercase, numbers and special characters etc.

·Avoid using the words from dictionary. They can be cracked easily.

·Create a password such that it can be remembered. This avoids the need to write passwords somewhere, which is not advisable.

·A password must be difficult to guess.

Countermeasures for Choosing a Good Password and Safeguarding Passwords

·Do not use a password that represents you personal information like nicknames, phone numbers, date of birth etc.

· Change the password once in a month or when you suspect someone knows the password.

·Do not use a password that was used earlier.

·Be careful while entering password when someone is sitting beside you.

·Never write a password on paper to store it. The brain is the best place to store it.

· Do not reveal your password to anyone, not even to the system administrator.

· Store the passwords on computer with the help of an encryption utility.

·Do not use the name of things located around you as passwords for your account.

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Security Zones Basic to In-depth Home Computer Security Guide Page 21

Security Zones

IE uses a capabilities/trust model called Zone Security. In this model, Web sites are permitted to perform certain actions based on the following zones.

• Restricted sites Zone-This zone contains web sites that could potentially damage user’s data.

• Trusted sites zone-This zone contains web sites that user can trust not to damage his computer or data.

• Local Intranet Zone- This zone contains all web sites that are on organization’s intranet.

• Internet Zone- This zone contains all web sites that user haven’t placed in other zones.

Figure-12: Security zones in Internet Explorer

Each zone has an assigned security level (High, Medium, Medium-Low, or Low). Users can modify the security level for each zone, but IE will warn them if they attempt to assign a zone, a security level lower than the recommended minimum level.

Disable ActiveX and Java Scripts

Malicious web scripts can get to a web browser when a web developer sends such damaging code as part of the web server’s response. This malicious code is then executed on the host running the browser.

Unfortunately the problem is by disabling these features; the user may find it frustrating that certain sites can no longer be effectively browsed. If the user cannot live without being able to run these scripts, then an alternative is to use a commercial anti-virus scanner that affords some level of protection against malicious scripts.

Choose the following options for safety:

Open Internet Explorer.

On the menu select Tools à Internet Options.

• Click on the Security tab.

• With the Internet zone highlighted, click the Custom Level button.

• Make the following modifications to the Internet zone:

• Under ActiveX controls and plug-ins, set Script ActiveX controls marked safe for scripting to Disable

• Under Scripting, set Active scripting to Disable (This will disable all scripting, including ActiveX. If this impacts required functionality, change the setting to Prompt)

• Under Scripting, set Scripting of Java applets to Disable

By default Trusted sites zone is assigned low security level, since this zone is intended for highly trusted sites, such as the sites of trusted business partners. User can also customize the settings by clicking on Custom level tab.

To add sites to this zone

• Click on Trusted sites icon

• Click on sites tab to add the trusted web site name

• Select Require server verification (HTTPS for all sites in this zone - This ensures that connections to the site are completely secure

• By default, the Restricted sites zone is assigned High security level. Assign sites to this zone as described earlier.

• Click on OK to return to the Internet Options box, and then click OK.

Other Security Settings in IE

IE contains many other security-related settings. Guidance on implementing a few of particular interest is as follows:

• Open Internet Explorer

• On the menu select Tools Internet Options

• Click on the Advanced tab

• Under Security, check the box for Check for server certificate revocation. This causes IE to verify that a Web site’s digital certificate has not been revoked before accepting it as legitimate and current

• Under Security, check the box for Empty Temporary Internet Files folder when browser is closed. This causes IE to delete temporary files after the browser session is finished; these files could inadvertently contain sensitive information.

Figure-13: Other Security Settings for IE

• Click on the Privacy tab, and then click the Advanced button

• Check the Override automatic cookie handling box. This allows different settings to be made for handling first-party and third-party cookies

• Change the Third-party Cookies setting from Accept to Prompt.

This setting causes IE to prompt the user to accept each third-party cookie that is presented to the system.

For more information on Internet Explorer look at the home page of IE at

http://www.microsoft.com/windows/ie/default.mspx

Secure Site Identification

When buying online, the user must be sure doing business on secure Web sites. Unscrupulous "hackers" can exploit insecure sites to steal user’s personal and important information such as credit card number. This information could be used to steal user’s identity.

Most e-commerce Web sites secure user’s personal information by encrypting or scrambling the data. Netscape and Internet Explorer users can check Web site security by following these instructions:

1. Look for the Lock symbol

Check the status bar at the bottom of the Web browser window for an unbroken lock symbol. This means user’s personal information is scrambled, and no one can read it but the e-business he has contacted.

2. Look for "https" in the Web Site's Address

Secure sites will change their beginning from "http" to “https” if the information is about to pass through a secure channel. The "s" stands for "secure" and indicates that information will travel the Internet in encrypted form.

Since user’s data is encrypted or scrambled, it can't be read during transmission. For example in www.hotmail.com when user enters the login and password information, the address bar indicates a change from “http” to “https” and also shows the following message before forwarding the information See Figure-13.

Figure -14: Message for secure connection

This warning message is generally ignored by the user or they just select it not to show in future, which is a bad practice. Whenever a security confirmation is made, user should verify the server’s digital certificate.

Check the Certificate

Double-click on the lock symbol to view the security certificate. Make sure the certificate is "Issued to" the Web site and the "Valid from" dates are current. User can also see the certificate from File à Properties and then choose certificates.

Figure-15: Checking the validity of a certificate

The certificate should be checked for the issuer, to whom it has been issued and validity period of the issued certificate (as shown in the figure-14 above).

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Mozilla Firefox Basic to In-depth Home Computer Security Guide Page 20

Mozilla Firefox:

This is the second most popular web browser that people use to access the Internet and
consequently needs coverage as well. The following instructions are for Mozilla Firefox running on a Microsoft Windows machine. The most popular version 1.5 and 2.0 all offers.

1. Pop-up Blockers:

As with IE, Mozilla Firefox, henceforth Firefox, also provides a Pop-up blocker. This can be accessed by clicking 'Tools|Options' menu and then clicking the 'Content' tab. Check the 'Block pop-up windows' check box and then click on the 'Exceptions' button to add a few websites from whom pop-ups may be allowed.

2. Java Script Control:

Java Scripts are used to provide the active content of a website. Since they are based on the principle of triggering a piece of program depending on the user input, they execute the moment a user clicks or inputs some data anywhere in the page. This is one of the methods used by malicious code programmers to get into a system and thus poses a threat. Firefox allows for the control of the Java Script execution. Click on the 'Tools|Options' menu item and then click on the 'Content' tab and check the 'Enable Java Script' check box. The default setup provided by Firefox should offer sufficient functionality and need not be worried about to tinker with.

3. History:

The access to the settings of the history of pages visited is held in the 'Privacy' tab of the Firefox options. It is advised to change the 'Remember visited pages for the last ___ days' box to a 0 (zero) value. Uncheck the 'Remember what I enter in forms and the search bar' box. This guarantees that none of your searches are stored in your cache that may be accessed by someone else.

4. Cookies:

Access to the cookies settings can be found in the 'Privacy' tab of the Firefox options. Firefox offers control of cookies by allowing the user the choose whether or not to accept cookies at all. A user may choose the 'Exceptions' and then choose to allow, temporarily allow or block cookies from a website. This setting is offered irrespective of the user's choice to allow/disallow a cookie. User discretion is advised here to allow or cookies at all and then give selective accept/deny to cookies.

5. Private Data:

Firefox allows you to clear all private data, Browsing History, Download History, Saved Forms Information etc. Automatically every time you close a session rather than you manually doing it. We can achieve this by clicking the 'Tools|Options' menu item and then clicking the 'Privacy' tab. Under the 'Private Data' section, check the 'Always clear my private data when I close Firefox' check box. The 'Settings' control offers you the control of what gets deleted upon every exit. Remember to check the cookies to be cleared. However, whether or not to clear the saved passwords depends on the user's preference to use the Password Manager facility. The 'Ask me before clearing private data' option prompts you to decide to clear private data at session close. A check mark indicates a prompt each time st session close.

Countermeasures for using the browsers safely

•Maintain an updated operating system with all security patches installed.

• Update the web browser before browsing the net.

• Run the anti-spy ware program depending upon the usage of the system.

Note: Spy ware is software that gathers information about a user while browsing the Internet and transmits the information to an individual who is responsible for introducing spy ware into the system.

• Maintain an updated AntiVirus software to protect the system from viruses.

• Set the operating system to display file extensions. For Microsoft Windows the settings should be made as shown below.

Go to My Computer --> Tools --> Folder Options -->In the View tab un check the option Hide file extensions for known file types.

• Always use trusted websites for browsing.

• Do not give your personal information over Internet.

• Avoid filling forms that came through email that ask for personal information.

• Always ensure that website offers security before submitting personal information through web browser. This can be done by checking the web address in the address bar which should begin with “https://” rather than “http://”.

• Do not click on the web link that has come via email. Instead go to main website by typing the address in the address bar.

• Never open a link in an email that asks for updating account/personal information.

• Avoid Phishing scams.

Note : Phishing is a process of attracting Internet users to a fake Web site by using authentic looking email with the real organization's logo, in an attempt to steal passwords, personal information, or for introducing virus in to the system.

• Block pop up windows while browsing Internet. Some pop-up messages may contain helpful information but most of the time they are advertisements with possibly some hidden code which is introduced by a hacker.

• Always clear private data after completing Internet browsing and do NOT save your login information.

•Always keep the firewall on.

• Turn off the computer or disconnect it from the network when not in use.

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Securing Web Browser Basic to In-depth Home Computer Security Guide Page 19

Securing Web Browser

Web browsers are capable of parsing active code in many forms, including JavaScript, ActiveX, and Java code. These are automatically downloaded and executed by web browser. Malicious individuals often take advantage of this to attack systems, distribute malicious code, or negatively impact systems. Microsoft Internet Explorer (IE) is installed as a default component of Windows Operating System and is closely integrated with it. Because of this, an exploitation of IE can seriously impact the underlying Windows installation, so it is critical to stay current with all IE updates. IE updates can be acquired through the Windows Update and Automatic updates features as described earlier.

Need for Securing the Browser

Since Internet Browser is the primary interface through which users connect to the Internet, there is a need to secure the web browser. Increasing the security of the browser, allows us to access trusted sites while disallowing access to possibly harmful ones.

Browser setting for Internet Explorer and Mozilla Firefox

Microsoft Internet Explorer

We shall briefly discuss the various security settings that Microsoft Internet Explorer (IE) offers. Owing to little difference in the versions of IE, we shall discuss the versions up to and including IE6.0 and IE7.0 separately.

1. Pop-up Blockers:

In IE6.0, click on Tools Pop-up Blocker. Turn on the pop-up blocker. The previously greyed 'Popup Blocker Settings' will be activated. If the pop-up blocker was already active then all you need is to look into the settings. It is advised to keep this list empty (i. e. block all pop-ups) and as you browse the web you will get notifications of any blocked web pages and you may then choose to let a few legitimate pop-ups through. This allows you control over the unwanted, annoying and possibly malicious pop-ups from opening. The 'Filter Level' in the pop-up blocker setting lets you control the extent of pop-up blocker intervention. For more information on pop-ups click on the 'Pop-up Blocker FAQ' at the lower left corner of the 'Pop-up Blocker Settings' window.

2. Trusted and Untrusted Websites:

Click on Tools|Internet Options to open the options window of IE. Click on the Security tab to open the security settings related to web pages. On this page you will have the choice of rating websites based on the suitability of the website contents. The 'Intranet Sites' are not of much use in the home environment. 'Trusted Sites' are the sites that you prefer to have relaxed access criteria. The 'Restricted Sites' are those whose content are inappropriate to be viewed and are consequently blocked if attempts to access these are initiated. 'Internet' encompassed the websites that are not put into any of these categories. Adding of websites to 'Trusted' and 'Restricted' areas is just a matter
of clicking the 'Sites' control and keying in the address of the website.

A note of caution though is to be remembered. A 'HIGH' security level provides high security at the cost of functionality. Similarly, a 'LOW' security level offers high functionality at the cost of security. Consequently, both these settings should be used with sound judgment.

3. Privacy Settings:

A website sets cookies (files that store user related information in your computer) to provide for added functionality in terms of access to the website content. However, since these cookies store information such as credit card details from an on line e-commerce site or user names and passwords, they need to be given a thought on whether or not a cookie should be allowed to be set by a website. The 'Privacy' tab in the IE6.0 options window ( Tools|Internet Options) offer for 6 levels of settings with increasing privacy protection. The 'Low' level is least intrusive but also least secure. Contrastingly, the 'Block All Cookies' setting block any cookie from being set and prevents websites from reading the existing cookies as well.

It is advised to delete all cookies those have been set by a website at the end of every browsing session. One can achieve this objective by clicking the 'Delete Cookies' command button on the 'General' tab of the options window.

4. Content Advisor:

The content advisor allows users view a website depending upon the content of the website. The content filtering is done on the following four criteria: Language, Nudity, Sex and Violence. These are particularly useful for restricting access to certain websites when a child is accessing the Internet. Click on the 'Content' tab of the IE potions window and then click on the 'Enable' button in the 'Content Advisor' section. In the window that opens, move the slider bars to adjust the extent of permissible content. The 'Approved Sites' tab lists those websites that are allowed irrespective of the settings in the 'Ratings' tab.

5. Private Data:

It is advisable to clear the cached cookies, pages visited and the temporary information created during a browser session. This results in clearing of information that would otherwise be left back in your system and might be used by a malicious user should he find an entry into your system. We can do this by opening the IE options window and click on the following entries:

• Delete Cookies

• Delete Files

• Clear History

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Physical Security Basic to In-depth Home Computer Security Guide Page 18

Physical Security

The first step in security is considering the physical security of the PC. Maintenance of physical security depends on the location and the budget. Some of the methods by which physical security is provided to the computers are:

·Computer Locks

Now a days PC's are available with a locking feature, which contains a socket in front of the case to unlock and lock the case. This helps us in preventing unauthorized users gain access to the hardware of the PC and also it prevents them booting the system with their own floppy or hardware.

·BIOS Security

BIOS (Basic Input Output System) are built in software, which describes what a computer can do without accessing the programs on the disk. It contains a code which can control the keyboards, monitor, serial and parallel communications and some other functions. BIOS come with a ROM chip in the computer which ensures that it will not be affected in case of disk failures.

Setting BIOS password prevents the unauthorized users from rebooting and manipulating the system. This provides a low level of security as someone can disconnect the batteries and access the BIOS with manufacturers default passwords. But it takes some time for unauthorized users to open case and accessing BIOS which leaves some traces of tampering.

·Many organizations now a days provide tracking and recovery services. These work with the help of software agents in the computer. Whenever a thief connects to the Internet, automatically without his knowledge IP address of the system or the phone number through which he is connecting is sent to recovery service centre.

·A continuous interruptible power supply should be provided to the systems in order to prevent loss of unsaved data during power failures.

·The systems should be placed in a room which is dust free and has a good ventilation to avoid overheating of CPU.

·The PC keys should be secured and not left unattended.

·Do not plug computer directly to the wall outlet as power surges may destroy computer. Instead use a genuine surge protector to plug a computer.

·Check the system input power supply and grounding at least annually to ensure that it meets the manufacturer’s specification.

·Static electricity may affect the integrity and reliability of data and programs processed and stored on equipment, hence antistatic devices should be installed.

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