Computer Security Basics David Yo

Computer Security Basics

David Young (Cyclonal Pharmaceutics Inc.)

The cardinal rule of security is that………. No one thing makes a computer secure.

Making a computer secure requires a list of different actions for different reasons.
There is a secondary rule that says security is an ongoing process. No matter how well a system is designed, if it is never changed that gives any potential infiltrator all the time in the world to examine the security for flaws.
The information described here is neither detailed nor comprehensive. This should, however, serve as a good overview of the types of security measures sometimes taken. What measures are appropriate are best determined on a case by case basis.
Physical security
Theft is the physical threat of most concern and rightfully so. Keeping rooms locked is a good idea, but not always feasible. Keeping computers locked to a wall or table is a good deterrent against a casual, shoplifting style, theft but it will not deter a professional with a shopping list. We have seen a thief use a crow bar to remove a computer along with a portion of the formica table top (they were then foolish enough to take it to a repair shop with the table top still attached). There are very loud alarms which sound when the power cable is unplugged. A combination of locks and alarms is an excellent theft prevention system for computer labs which must be publicly accessible, particularly at late hours.
Computer hardware is protected from fire damage by smoke detectors and sprinkler systems just like any other equipment. Computers are unique in that the most costly damage is the loss of data which can be prevented by storing back up tapes in remote locations.
Surge protectors and uninterruptable power supplies are a low cost investment that can save very costly equipment damage. These are particularly important if the computer must be used continuously or if your region is prone to severe thunder storms or frequent power outages. Some surge protectors have the ability to protect the phone line going to a modem also. The modem and mother board can be more readily damaged by lightning hitting a phone line than by lightning hitting the power lines because the computer power supply provides a minimal amount of protection.
Data integrity
Backing up data is the single most important step in preventing data loss. Entire companies have gone out of business due to losing valuable information. An enormous amount of man hours are spent every year reproducing information which was lost in some manner. Backups can be on removable disks, tapes, paper printouts or other computer systems. It is important to periodically put copies of these backups in remote physical locations to prevent losing the original and back up data through fire, etc.

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In today's world, virus protection is a necessity for any PC or Macintosh and viruses are starting to appear on UNIX systems also. No system is completely safe from viruses since manufacturers have inadvertantly shipped new computers with viruses on the hard drive and minted CDs with viruses.
For very important data, RAID systems are used. RAID stands for "Redundant Array of Inexpensive Disks". A raid system is a computer with eight or more hard drives and software for storing data on those drives. Every byte of data is spread across all of these drives along with a parity bit that tells if it was an odd or even byte. In the event that a disk fails, it's contents can be completely reconstructed from the data on the other seven disks. This is a good way to store critical data which could not be reproduced, but the expense may not be justified otherwise.
Data security
The primary threat to data security is illegal computer hackers. Studies show that the largest percentage of hackers are young men motivated by status with other hackers, malicious intent or the excitement of a challenging game. There have also been even more harmful cases of corporate spying and embezzlement of funds.
Accounts on both multiuser machines and micro computers can be protected by passwords. Passwords can be very effective or not effective at all. Insecure password includes ones that are easily guessed, never changed, shared or written down somewhere. Some systems, particularly UNIX, have password files which are encrypted but readable by all users. Hackers have developed automated programs, such as "crack", to break the passwords in these files by raw brute force, trial & error techniques. Since it could take months to crack well-chosen passwords, some systems use a password aging system that requires all users to set new passwords periodically. There are also programs to prevent users from setting easily guessed passwords such as words in the dictionary, common names or permutations on the account name.
Systems holding data belonging to multiple users, such as UNIX or Windows NT, set an owner for each file and permissions defining who is allowed to read or write to it. Many hacker attacks are centered around finding flaws in the file permission system. There are ways to set default permissions and ways to control how much individual users can control their own file permissions.
Since most security attacks are now initiated from a remote location via the network, many organizations now separate their internal networks from the internet with a firewall. A firewall is a piece of software running on a dedicated machine with two network boards. The software can filter which network traffic is allowed to pass between the internal and external networks. This is a very effective security measure, but there is an unfortunate tendency for organizations to make the firewall their only security measure making any breach of security across the firewall a breach for every machine in the whole organization. An even higher level of security can be acheived by not having any connection between the internal network and the internet or not even having an internal network.
Data encryption provides a second layer of security. Once someone gains access to data, that data is useless if it has been scrambled by an encryption program which requires a second password to unscramble it. Passwords themselves should always be stored in an encrypted form. Today's encryption systems are similar to military code systems but not as sophisticated as the systems used by the armed forces. Almost all encrypted data can be unencrypted without the password by the use of a very large amount of time on very powerful computers. Security is provided by making the encryption complex enough that no one would be likely to have enough computer power to break say a message about the merger next month in less than six months, at which time the message is no longer valuable.
KEEP GOING!





There must always be someone able to fix a computer system by using a second password protected account called "system", "administrator", "root" or "super user" which bypasses the file permission system. One of the most serious security attacks is one which gains the password to this account. As well as particularly stringent security for this account, the encryption systems mentioned above ensure that there is a second layer of protection against this type of attack. This also provides for a segmented internal security system, if such is necessary.
Email is particularly insecure. Mail messages are simple ascii files that travel across the network where no password is necessary to get to them. Email is easily forged and can be altered. Of course, no one would have any particular reason for tampering with many personal messages, but people conducting sensitive business transactions over email would be wise to use some sort of email encryption system, such as PGP. These systems have several functions including encrypting the message itself, verifying who sent the message and verifying that it was not tampered with.
Audit trails are a means for the system administrators to find out if security has been breached and how much damage was done. Audit trails are records made by various pieces of software to log who logged into a system, from where and what files were accessed.
How Hackers get in
Here is the typical sequence of steps used to gain illegal entry into a computer system.
1. Learn about the system. Trying to connect to a system using networking utilities like telnet and ftp will be unsuccessful without a password, but even unsuccessful logins will often still display the machine manufacturer, and version of the operating system.
2. Look for openings. Try known security flaws on that particular machine and operating system. Unless the system administrator is very diligent about installing security patches, many machines have openings in the security just waiting to be found.
3. Try sniffing to get a password. Sniffing is when a machine has software to watch all of the network traffic and saves the messages corresponding to a valid user entering their password from a remote location.
4. Try spoofing. Many machines share disks with other machines that are classified as "trusted hosts". In order to share the data on these disks the two machines must communicate without a password. Spoofing is when someone configures a third machine to use the network address of one of the trusted hosts to impersonate that machine. If the spoofing machine responds faster than the true trusted host, communications will be carried out with it unnoticed. Spoofing requires that the infiltrator have physical access to the network in a location that falls close to the target machine in the network topology, which usually means being physically close to the target machine.
5. Get into the system and cover tracks. Once one of the above techniques is successful in gaining access to the system, the first order of business is to alter any records that would reveal the presence of an illegal

Kết quả (Việt) 1:

Khái niệm cơ bản bảo mật máy tính David Young (Cyclonal dược phẩm Inc)Các quy tắc hồng y của bảo mật là... Không có một điều làm cho một máy tính an toàn.Làm cho một máy tính an toàn đòi hỏi một danh sách các hành động khác nhau cho các lý do khác nhau.Đó là một quy tắc thứ hai nói rằng bảo mật là một quá trình liên tục. Không có vấn đề tốt như thế nào một hệ thống được thiết kế, nếu nó không bao giờ thay đổi đó cung cấp cho bất kỳ infiltrator tiềm năng tất cả thời gian trên thế giới để kiểm tra an ninh cho sai sót.Thông tin mô tả ở đây là không chi tiết, cũng không toàn diện. Điều này sẽ, Tuy nhiên, phục vụ như là một tổng quan tốt đẹp của các loại biện pháp an ninh đôi khi thực hiện. Những gì các biện pháp được thích hợp tốt nhất được xác định trên cơ sở của trường hợp.Bảo mật vật lýTrộm cắp là vật lý mối đe dọa của hầu hết các mối quan tâm và rightfully như vậy. Giữ phòng bị khóa là một ý tưởng tốt, nhưng không phải luôn luôn khả thi. Giữ máy tính khóa để một bức tường hoặc bàn là một biện pháp chống tốt chống lại một phong cách giản dị, trộm, trộm cắp, nhưng nó sẽ không ngăn chặn một chuyên nghiệp với một danh sách mua sắm. Chúng tôi đã thấy một tên trộm một con quạ thanh sử dụng để loại bỏ máy tính cùng với một phần của đầu bảng formica (họ được sau đó ngu si, đủ để mang nó đến một cửa hàng sửa chữa với đầu bảng vẫn còn đính kèm). Không có báo động rất lớn mà âm thanh khi cáp điện được cắm phít. Một sự kết hợp của ổ khóa và hệ thống báo động là một hệ thống công tác phòng chống trộm cắp tuyệt vời cho phòng thí nghiệm máy tính phải truy cập công cộng, đặc biệt là ở cuối giờ.Máy vi tính được bảo vệ từ cháy, thiệt hại cháy và chữa cháy tự động hệ thống cũng giống như bất kỳ thiết bị khác. Máy tính là duy nhất trong đó những thiệt hại tốn kém nhất là sự mất mát dữ liệu mà có thể được ngăn chặn bằng cách lưu trữ sao lưu băng ở địa điểm từ xa.Bảo vệ tăng xung áp và nguồn cung cấp nguồn điện là một đầu tư chi phí thấp mà có thể tiết kiệm rất tốn kém thiết bị thiệt hại. Đây là đặc biệt quan trọng nếu máy tính phải được sử dụng liên tục hoặc nếu khu vực của bạn là dễ bị cơn bão sấm sét nghiêm trọng hay Cúp điện thường xuyên. Một số bảo vệ sự đột biến có khả năng để bảo vệ đường dây điện thoại đi với một modem cũng. Hội đồng quản trị modem và mẹ có thể được dễ dàng hơn bị hư hại bởi sét đánh một đường dây điện thoại hơn bởi sét đánh các đường dây điện vì cung cấp năng lượng máy tính cung cấp một số tiền tối thiểu của bảo vệ.Toàn vẹn dữ liệuSao lưu dữ liệu là bước duy nhất quan trọng nhất trong việc ngăn ngừa mất dữ liệu. Toàn bộ công ty đã đi ra khỏi kinh doanh do mất thông tin giá trị. Một số lượng lớn của người đàn ông giờ được chi tiêu hàng năm tái tạo thông tin mà mất đi trong một số cách thức. Sao lưu có thể trên ổ đĩa, băng, bản in giấy hoặc các hệ thống máy tính khác. Nó là quan trọng để định kỳ đặt bản sao của các bản sao lưu trong vị trí thực tế từ xa để ngăn chặn mất bản gốc và sao lưu dữ liệu thông qua lửa, vv. Tiếp tục đi!Trong thế giới ngày nay, bảo vệ chống virus là một điều cần thiết cho bất kỳ máy tính hoặc Macintosh và vi rút đang bắt đầu xuất hiện trên hệ thống UNIX cũng. Không có hệ thống là hoàn toàn an toàn từ vi rút kể từ khi nhà sản xuất có inadvertantly vận chuyển mới máy tính với vi rút trên ổ đĩa cứng và đĩa CD đúc với vi rút.Đối với dữ liệu rất quan trọng, cuộc tấn công hệ thống được sử dụng. RAID là viết tắt của "Dự phòng mảng của chi phí thấp đĩa". Một hệ thống raid là một máy tính với tám hoặc nhiều ổ đĩa cứng và phần mềm để lưu trữ dữ liệu trên các ổ đĩa đó. Mỗi byte dữ liệu được lan truyền trên tất cả các ổ đĩa cùng với bit chẵn lẻ cho biết nếu nó là một byte lẻ hoặc thậm chí. Trong trường hợp đó một đĩa thất bại, đó là nội dung có thể được hoàn toàn tái tạo từ các dữ liệu trên bảy đĩa. Đây là một cách tốt để lưu trữ dữ liệu quan trọng mà có thể không được sao chép, nhưng chi phí có thể không được chứng minh bằng cách khác. Bảo mật dữ liệuCác mối đe dọa chính để bảo mật dữ liệu là bất hợp pháp máy tính tin tặc. Nghiên cứu cho thấy rằng tỷ lệ phần trăm lớn nhất của tin tặc là người đàn ông trẻ thúc đẩy bởi tình trạng với tin tặc khác, độc hại intent hoặc sự phấn khích của một trò chơi đầy thử thách. Hiện cũng đã là nhiều hơn có hại trường hợp các gián điệp công ty và các tham ô tiền.Accounts on both multiuser machines and micro computers can be protected by passwords. Passwords can be very effective or not effective at all. Insecure password includes ones that are easily guessed, never changed, shared or written down somewhere. Some systems, particularly UNIX, have password files which are encrypted but readable by all users. Hackers have developed automated programs, such as "crack", to break the passwords in these files by raw brute force, trial & error techniques. Since it could take months to crack well-chosen passwords, some systems use a password aging system that requires all users to set new passwords periodically. There are also programs to prevent users from setting easily guessed passwords such as words in the dictionary, common names or permutations on the account name.Systems holding data belonging to multiple users, such as UNIX or Windows NT, set an owner for each file and permissions defining who is allowed to read or write to it. Many hacker attacks are centered around finding flaws in the file permission system. There are ways to set default permissions and ways to control how much individual users can control their own file permissions.Since most security attacks are now initiated from a remote location via the network, many organizations now separate their internal networks from the internet with a firewall. A firewall is a piece of software running on a dedicated machine with two network boards. The software can filter which network traffic is allowed to pass between the internal and external networks. This is a very effective security measure, but there is an unfortunate tendency for organizations to make the firewall their only security measure making any breach of security across the firewall a breach for every machine in the whole organization. An even higher level of security can be acheived by not having any connection between the internal network and the internet or not even having an internal network.Data encryption provides a second layer of security. Once someone gains access to data, that data is useless if it has been scrambled by an encryption program which requires a second password to unscramble it. Passwords themselves should always be stored in an encrypted form. Today's encryption systems are similar to military code systems but not as sophisticated as the systems used by the armed forces. Almost all encrypted data can be unencrypted without the password by the use of a very large amount of time on very powerful computers. Security is provided by making the encryption complex enough that no one would be likely to have enough computer power to break say a message about the merger next month in less than six months, at which time the message is no longer valuable.
KEEP GOING!





There must always be someone able to fix a computer system by using a second password protected account called "system", "administrator", "root" or "super user" which bypasses the file permission system. One of the most serious security attacks is one which gains the password to this account. As well as particularly stringent security for this account, the encryption systems mentioned above ensure that there is a second layer of protection against this type of attack. This also provides for a segmented internal security system, if such is necessary.
Email is particularly insecure. Mail messages are simple ascii files that travel across the network where no password is necessary to get to them. Email is easily forged and can be altered. Of course, no one would have any particular reason for tampering with many personal messages, but people conducting sensitive business transactions over email would be wise to use some sort of email encryption system, such as PGP. These systems have several functions including encrypting the message itself, verifying who sent the message and verifying that it was not tampered with.
Audit trails are a means for the system administrators to find out if security has been breached and how much damage was done. Audit trails are records made by various pieces of software to log who logged into a system, from where and what files were accessed.
How Hackers get in
Here is the typical sequence of steps used to gain illegal entry into a computer system.
1. Learn about the system. Trying to connect to a system using networking utilities like telnet and ftp will be unsuccessful without a password, but even unsuccessful logins will often still display the machine manufacturer, and version of the operating system.
2. Look for openings. Try known security flaws on that particular machine and operating system. Unless the system administrator is very diligent about installing security patches, many machines have openings in the security just waiting to be found.
3. Try sniffing to get a password. Sniffing is when a machine has software to watch all of the network traffic and saves the messages corresponding to a valid user entering their password from a remote location.
4. Try spoofing. Many machines share disks with other machines that are classified as "trusted hosts". In order to share the data on these disks the two machines must communicate without a password. Spoofing is when someone configures a third machine to use the network address of one of the trusted hosts to impersonate that machine. If the spoofing machine responds faster than the true trusted host, communications will be carried out with it unnoticed. Spoofing requires that the infiltrator have physical access to the network in a location that falls close to the target machine in the network topology, which usually means being physically close to the target machine.
5. Get into the system and cover tracks. Once one of the above techniques is successful in gaining access to the system, the first order of business is to alter any records that would reveal the presence of an illegal