Basic Computer Security Precautions
Research has shown that users are unlikely (as in "you are not likely to be struck by lightning") to be the victim of an Internet security attack. They are, however, vulnerable to computer virus infections, hardware failures, and to inquisitive students and co-workers. Statistics show that most security breaches are the result of insider misconduct, as opposed to hacking by outsiders. Often this insider misconduct is the result of ignorance rather than malfeasance.
Users should take reasonable precautions to protect the files on their computers, and to protect data as it transits the Internet. For each user of the Rhodes network, the reasonable level of precautions may be different, and it depends on that user's needs.
All users should take the following basic security precautions:
- Back up important files.
- Use a virus scanner on your PC.
- Regularly check for, download, and INSTALL security patches from the vendors of the software on your PC.
- Use a secure password for network access controls.
- Ensure permissions are set properly on files that can be accessed by others.
- If your files are being stored on a server that you do not control, for example a web or ftp server, and you expect there to be access restrictions (such as your files not being visible outside Rhodes or visible only to you) it would be wise to periodically check that these access restrictions are functioning as intended.
- Encrypt, or store off-line, files that are particularly sensitive.
- Do not send sensitive user identifications, such as address, phone number, personal data, or credit card number across the Internet unless it is encrypted at the source (prior to being sent across the Internet).
- Use an encryption program, such as Pretty Good Privacy (PGP), if you want e-mail to be private.
- Conduct some form of risk analysis to determine the cost effective level of security. At the very least this would be to establish what recourse you have, and what procedures you would follow, were you to discover that your credit card number has been compromised and is being abused.
Backing up files
The first basic precaution a user should take is to back up important files. This will not prevent a security incident or hardware failure, but it may reduce the impact if a user is involved in such an incident. On a different level, remember that data stored on your computer would probably be lost if the machine was stolen or destroyed by fire.
Which files should be backed up can easily be determined if a user imagines losing the original files. For example, if a user's files are stored on the local hard drive, what would the user lose that is important if the hard drive files were lost or there was a hardware failure?
Software can usually be reloaded, but a user's personal files may be lost permanently if they are not stored elsewhere.
How many backups a user should make and where they should be stored depends on how important the files are. For most users, one backup to floppy disks or to a hard drive on a separate computer is probably sufficient.
It should be noted that user files stored on central servers managed by the IT Division are backed up to tape on a regular and ongoing basis. Some of these servers make use of RAID technology and/or disk mirroring in order to eliminate problems associated with catastrophic hardware failure.
However, it would be foolish and risky to assume that such automated backups work properly at all times, or have taken place just before an important file is lost and just after it has been extensively modified. System backups concentrate on the bigger picture of how to recover an entire disk partition rather than on up to the minute versions of user files.
Users should exercise reasonable precautions in order to minimize the introduction and spread of computer viruses onto the Rhodes networks. Virus scanning software should be used to check any software downloaded from the Internet or obtained from any questionable source.
Using virus protection software means three things: having it installed on your computer; checking frequently for virus signature updates; and actually scanning the files on your PC.
Attachments received by email should be treated with caution. This means do not open email attachments from strangers no matter how interesting they may be. Be equally suspicious about any unexpected email attachment from somebody you do know -- it might have been sent without that persons knowledge from an infected machine.
All PC users at Rhodes using Microsoft Windows software should regularly look at:
The fourth basic security precaution that all users should take is to have a good password for the access controls to their network. Unlike backing up files, this action may prevent a security incident.
One of the more common methods to gain unauthorized access in a network is referred to as a "brute force" attack. Brute force attacks occur when a hacker makes repeated, continuous attempts to guess a user's password, perhaps using a special cracking program that makes use of commonly available word lists - including lists of the most commonly used passwords and Hungarian family names. Problematically, this can be done across the network or directly on the password database file stored on a server.
Packet sniffing is the process of using an electronic device to capture data (packets) as they travel across a network. The captured data are then deciphered (typically through brute force attacks) into readable text. If a user name and password are revealed through decoding of the captured information the account is cracked and the network compromised.
But the most common compromise to password security is much less technical: namely sloppy password practices. Most of Rhodes' user names are common knowledge - they are associated with your e-mail address! That leaves the user password as the crucial unknown to prevent intrusion. The security of a network is only as strong as its weakest link. While there are specific measures the IT Division can and will take to continue to enhance information security from a technical standpoint, network security is a responsibility we all share. Faculty, staff and students need to be acutely aware of the dangers posed by lax password policies.
A separate document is available that covers good password practice.
Another basic precaution that all users should take is to ensure that permissions on files that can be accessed by others are set properly.
An example of files that could be accessed by others are files in a Unix or Novell account. The Unix and Novell operating systems maintain a set of permissions on each file that establishes permission to read, write, or execute the file by the file owner, a group of users, or all users. If a user does not want other users to read his files, then the permissions for each file must be set to prevent this.
This is not just a concern for Unix or Novell users. As operating systems become more network capable, such as Windows NT, the same capabilities and concerns arise. In the case of Windows 95/98/NT and 2000, inadvertently allowing files to be shared over the network can all too easily occur.
Unprotected Windows networking shares can be exploited by intruders in an automated way to place tools on large numbers of Windows-based computers attached to the Internet. Because site security on the Internet is interdependent, a compromised system not only creates problems for the system's owner, but it is also threat to other sites on the Internet.
Several steps can be taken to prevent exploitation of the problem of unprotected Windows networking shares:
- Disable Windows networking shares in the Windows network control panel if the ability to share files is not needed. Or, you may choose to entirely disable NETBIOS over TCP/IP in the network control panel.
- When configuring a Windows share, require a password to connect to the share. The use of sound password practices is encouraged. It is also important to consider trust relationships between systems. Malicious code may be able to leverage situations where a vulnerable system is trusted by and already authenticated to a remote system.
- Restrict exported directories and files to the minimum required for an application. In other words, rather than exporting an entire disk, export only the directory or file needed. Export read-only where possible.
Users may elect to take further precautions for files that are particularly sensitive, such as copies of upcoming examination papers. If the concern is unauthorized disclosure, these files should be encrypted. Another alternative is to store files off-line from the network.
Remove all sensitive data from hard drives before equipment is transferred out of your department. This is especially important if equipment is being repaired off-site.
Protecting data in transit
Almost all Internet traffic is sent "in the clear." This means that it can be read by software on any host computer through which the network packets are routed without having to be de-crypted. This should be of little concern to most Internet users because most of the packets traveling on the Internet contain data that is not sensitive from the user's viewpoint, and is of no interest to Internet attackers.
Several types of information traveling across the network that are sensitive to users, and of interest to Internet attackers, are discussed in the following sections.
The first type of sensitive information traveling across the Internet is user name, password, and IP address combinations. These data are the primary targets of sniffer programs operated by Internet attackers. These are read by the sniffer program and typically recorded in a file intended to be retrieved later by the attacker. These combinations can then be used to break into the user's account. and from there the attacker can compromise the entire system.
A solution to this problem is to have these data sent across the Internet in a secure manner, such as by encrypting them first.
The most likely source of clear username/password problems is using FTP for retrieving files off a remote non-anonymous-ftp account, for example if you are visiting an institution and wish to transfer some of your research data from a server at Rhodes. Currently, an individual user cannot do anything about this, except, as noted above, to change passwords frequently and to use client software capable of encryption such as SSH, or web browsers that are SSL enabled and talking to a secure web server.
File and email encryption
Other types of information traveling across the Internet are sensitive user identifications, and files whose content is sensitive to the user.
Users should take one of two precautions, either encrypt the information or don't send it across the Internet.
Examples of sensitive user identifications are address, phone number, personal data, and perhaps most sensitive of all, credit card numbers.
In general, none of these data should be sent across the Internet unless they are encrypted at the source (prior to being sent across the Internet).
An example of a file that would possibly be sensitive to the user is e-mail containing personal information or sensitive work related information such as a newly set examination paper. If a user wants to ensure this information is kept confidential, then it must either be encrypted, or sent some other way (such as through old fashioned SAPO registered mail in a sealed envelope, or by courier). Pretty Good Privacy (PGP) is an e-mail encryption program available on the Internet that can provide encrypted e-mail.