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Text File | 2003-06-29 | 22KB | 863 lines

ZDDDDDDDDDDDDDDDDDD? IMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM; ZDDDDDDDDDDDDDDDDDD? 3 Founded By: 3 : Network Information Access : 3 Mother Earth BBS 3 3 Guardian Of Time 3D: 17APR90 :D3 NUP:> DECnet 3 3 Judge Dredd 3 : Judge Dredd : 3Text File Archives3 @DDDDDDDDBDDDDDDDDDY : File 24 : @DDDDDDDDDBDDDDDDDDY 3 HMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM< 3 3 IMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM; 3 @DDDDDDDDDDD6 Computer Viruses & Threats II GDDDDDDDDDDDY HMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM< $_Virus Prevention in General To provide general protection from attacks by computer viruses, unauthorized users, and related threats, users and managers need to eliminate or reduce vulnerabilities. A general summary of the vulnerabilities that computer viruses and related threats are most likely to exploit is as follows: - lack of user awareness - users copy and share infected software, fail to detect signs of virus activity, do not understand proper security techniques - absence of or inadequate security controls - personal computers generally lack software and hardware security mechanisms that help to prevent and detect unauthorized use, existing controls on multi-user systems can sometimes be surmounted by knowledgeable users - ineffective use of existing security controls - using easily guessed passwords, failing to use access controls, granting users more access to resources than necessary - bugs and loopholes in system software - enabling knowledgeable users to break into systems or exceed their authorized privileges - unauthorized use - unauthorized users can break in to systems, authorized users can exceed levels of privilege and misuse systems - susceptibility of networks to misuse - networks can provide anonymous access to systems, many are in general only as secure as the systems which use them As can be seen from this summary, virus prevention requires that many diverse vulnerabilities be addressed. Some of the vulnerabilities can be improved upon significantly, such as security controls that can be added or improved, while others are somewhat inherent in computing, such as the risk that users will not use security controls or follow policies, or the risk of unauthorized use of computers and networks. Thus, it may not be possible to completely protect systems from all virus-like attacks. However, to attain a realistic degree of protection, all areas of vulnerability must be addressed; improving upon some areas at the expense of others will still leave significant holes in security. To adequately address all areas of vulnerability, the active involvement of individual users, the management structure, and the organization in a virus prevention program is essential. Such a program, whether formal or informal, depends on the mutual cooperation of the three groups to identify vulnerabilities, to take steps to correct them, and to monitor the results. A virus prevention program must be initially based upon effective system computer administration that restricts access to authorized users, ensures that hardware and software are regularly monitored and maintained, makes backups regularly, and maintains contingency procedures for potential problems. Sites that do not maintain a basic computer administration program need to put one into place, regardless of their size or the types of computers used. Many system vendors supply system administration manuals that describe the aspects of a basic program. Once a basic administration program is in place, management and users need to incorporate virus prevention measures that will help to deter attacks by viruses and related threats, detect when they occur, contain the attacks to limit damage, and recover in a reasonable amount of time without loss of data. To accomplish these aims, attention needs to be focused on the following areas: - educating users about malicious software in general, the risks that it poses, how to use control measures, policies, and procedures to protect themselves and the organization - software management policies and procedures that address public-domain software, and the use and maintenance of software in general - use of technical controls that help to prevent and deter attacks by malicious software and unauthorized users - monitoring of user and software activity to detect signs of attacks, to detect policy violations, and to monitor the overall effectiveness of policies, procedures, and controls - contingency policies and procedures for containing and recovering from attacks General guidance in each of these areas is explained in the following sections. $_Education Education is one of the primary methods by which systems and organizations can achieve greater protection from incidents of malicious software and unauthorized use. In situations where technical controls do not provide complete protection (i.e., most computers), it is ultimately people and their willingness to adhere to security policies that will determine whether systems and organizations are protected. By educating users about the general nature of computer viruses and related threats, an organization can improve its ability to deter, detect, contain Users should be educated about the following: - how malicious software operates, methods by which it is planted and spread, the vulnerabilities exploited by malicious software and unauthorized users - general security policies and procedures and how to use them - the policies to follow regarding the backup, storage, and use of software, especially public-domain software and shareware - how to use the technical controls they have at their disposal to protect themselves - how to monitor their systems and software to detect signs of abnormal activity, what to do or whom to contact for more information - contingency procedures for containing and recovering from potential incidents User education, while perhaps expensive in terms of time and resources required, is ultimately a cost-effective measure for protecting against incidents of malicious software and unauthorized use. Users who are better acquainted with the destructive potential of malicious software and the methods by which it can attack systems may in turn be prompted to take measures to protect themselves. The purpose of security policies and procedures will be more clear, thus users may be more willing to actively use them. By educating users how to detect abnormal system activity and the resultant steps to follow for containing and recovering from potential incidents, organizations will save money and time if and when actual incidents occur. $_Software Management As shown by examples in File 1, one of the prime methods by which malicious software is initially copied onto systems is by unsuspecting users. When users download programs from sources such as software bulletin boards, or public directories on systems or network servers, or in general use and share software that has not been obtained from a reputable source, users are in danger of spreading malicious software. To prevent users from potentially spreading malicious software, managers need to - ensure that users understand the nature of malicious software, how it is generally spread, and the technical controls to use to protect themselves - develop policies for the downloading and use of public- domain and shareware software - create some mechanism for validating such software prior to allowing users to copy and use it - minimize the exchange of executable software within an organization as much as possible - do not create software repositories on LAN servers or in multi-user system directories unless technical controls exist to prevent users from freely uploading or downloading the software The role of education is important, as users who do not understand the risks yet who are asked to follow necessarily restrictive policies may share and copy software anyway. Where technical controls cannot prevent placing new software onto a system, users are then primarily responsible for the success or failure of whatever policies are developed. A policy that prohibits any copying or use of public-domain software may be overly restrictive, as some public domain programs have proved to be useful. A less restrictive policy would allow some copying, however a user might first require permission from the appropriate manager. A special system should be used from which to perform the copy and then to test the software. This type of system, called an isolated system, should be configured so that there is no risk of spreading a potentially malicious program to other areas of an organization. The system should not be used by other users, should not connect to networks, and should not contain any valuable data. An isolated system should also be used to test internally developed software and updates to vendor software. Other policies for managing vendor software should be developed. These policies should control how and where software is purchased, and should govern where the software is installed and how it is to be used. The following policies and procedures are suggested: - purchase vendor software only from reputable sources - maintain the software properly and update it as necessary - don't use pirated software, as it may have been modified - keep records of where software is installed readily available for contingency purposes - ensure that vendors can be contacted quickly if problems occur - store the original disks or tapes from the vendor in a secure location $_Technical Controls Technical controls are the mechanisms used to protect the security and integrity of systems and associated data. The use of technical controls can help to prevent occurrences of viruses and related threats by deterring them or making it more difficult for them to gain access to systems and data. Examples of technical controls include user authentication mechanisms such as passwords, mechanisms which provide selective levels of access to files and directories (read-only, no access, access to certain users, etc.), and write-protection mechanisms on tapes and diskettes. The different types of technical controls and the degree to which they can provide protection and deterrence varies from system to system, thus the use of specific types of controls is discussed in the following files. However, the following general points are important to note: - technical controls should be used as available to restrict system access to authorized users only - in the multi-user environment, technical controls should be used to limit users' privileges to the minimum practical level; they should work automatically and need not be initiated by users - users and system managers must be educated as to how and when to use technical controls - where technical controls are weak or non-existent (i.e., personal computers), they should be supplemented with alternative physical controls or add-on control mechanisms Managers need to determine which technical controls are available on their systems, and then the degree to which they should be used and whether additional add-on controls are necessary. One way to answer these questions is to first categorize the different classes of data being processed by a system or systems, and then to rank the categories according to criteria such as sensitivity to the organization and vulnerability of the system to attack. The rankings should then help determine the degree to which the controls should be applied and whether additional controls are necessary. Ideally, those systems with the most effective controls should be used to process the most sensitive data, and vice-versa. As an example, a personal computer which processes sensitive employee information should require add-on user authentication mechanisms, whereas a personal computer used for general word processing may not need additional controls. It is important to note that technical controls do not generally provide complete protection against viruses and related threats. They may be cracked by determined users who are knowledgeable of hidden bugs and weaknesses, and they may be surmounted through the use of Trojan horse programs, as shown by examples in File 1. An inherent weakness in technical controls is that, while deterring users and software from objects to which they do not have access, they may be totally ineffective against attacks which target objects that are accessible. For example, technical controls may not prevent an authorized user from destroying files to which the user has authorized access. Most importantly, when technical controls are not used properly, they may increase a system's degree of vulnerability. It is generally agreed that fully effective technical controls will not be widely available for some time. Because of the immediate nature of the computer virus threat, technical controls must be supplemented by less technically-oriented control measures such as described in this chapter. $_General Monitoring An important aspect of computer viruses and related threats is that they potentially can cause extensive damage within a very small amount of time, such as minutes or seconds. Through proper monitoring of software, system activity, and in some cases user activity, managers can increase their chances that they will detect early signs of malicious software and unauthorized activity. Once the presence is noted or suspected, managers can then use contingency procedures to contain the activity and recover from whatever damage has been caused. An additional benefit of general monitoring is that over time, it can aid in determining the necessary level or degree of security by indicating whether security policies, procedures, and controls are working as planned. Monitoring is a combination of continual system and system management activity. Its effectiveness depends on cooperation between management and users. The following items are necessary for effective monitoring: - user education - users must know, specific to their computing environment, what constitutes normal and abnormal system activity and whom to contact for further information - this is especially important for users of personal computers, which generally lack automated methods for monitoring - automated system monitoring tools - generally on multi- user systems, to automate logging or accounting of user and software accesses to accounts, files, and other system objects - can sometimes be tuned to record only certain types of accesses such as "illegal" accesses - anti-viral software - generally on personal computers, these tools alert users of certain types of system access that are indicative of "typical" malicious software - system-sweep programs - programs to automatically check files for changes in size, date, or content - network monitoring tools - as with system monitoring tools, to record network accesses or attempts to access The statistics gained from monitoring activities should be used as input for periodic reviews of security programs. The reviews should evaluate the effectiveness of general system management, and associated security policies, procedures, and controls. The statistics will indicate the need for changes and will help to fine tune the program so that security is distributed to where it is most necessary. The reviews should also incorporate users' suggestions, and to ensure that the program is not overly restrictive, their criticisms. $_Contingency Planning The purpose of contingency planning with regard to computer viruses and related threats is to be able to contain and recover completely from actual attacks. In many ways, effective system management that includes user education, use of technical controls, software management, and monitoring activities, is a form of contingency planning, generally because a well-run, organized system or facility is better able to withstand the disruption that could result from a computer virus attack. In addition to effective system management activities, managers need to consider other contingency procedures that specifically take into account the nature of computer viruses and related threats. Possibly the most important contingency planning activity involves the use of backups. The ability to recover from a virus attack depends upon maintaining regular, frequent backups of all system data. Each backup should be checked to ensure that the backup media has not been corrupted. Backup media could easily be corrupted because of defects, because the backup procedure was incorrect, or perhaps because the backup software itself has been attacked and modified to corrupt backups as they are made. Contingency procedures for restoring from backups after a virus attack are equally important. Backups may contain copies of malicious software that have been hiding in the system. Restoring the malicious software to a system that has been attacked could cause a recurrence of the problem. To avoid this possibility, software should be restored only from its original media: the tapes or diskettes from the vendor. In some cases, this may involve reconfiguring the software, therefore managers must maintain copies of configuration information for system and application software. Because data is not directly executable, it can be restored from routine backups. However, data that has been damaged may need to be restored manually or from older backups. Command files such as batch procedures and files executed when systems boot or when user log on should be inspected to ensure that they have not been damaged or modified. Thus, managers will need to retain successive versions of backups, and search through them when restoring damaged data and command files. Other contingency procedures for containing virus attacks need to be developed. The following are suggested; they are discussed in more detail in following files: - ensure that accurate records are kept of each system's configuration, including the system's location, the software it runs, the system's network and modem connections, and the name of the system's manager or responsible individual - create a group of skilled users to deal with virus incidents and ensure that users can quickly contact this group if they suspect signs of viral activity - maintain a security distribution list at each site with appropriate telephone numbers of managers to contact when problems occur - isolate critical systems from networks and other sources of infection - place outside network connections on systems with the best protections, use central gateways to facilitate rapid disconnects -JUDGE DREDD/NIA [OTHER WORLD BBS] .