Choosing the right network media for the right circumstances can have a good influence on overall network security. Although the options are often limited by the required data throughput and cable lengths, there are security related factors that should be evaluated when choosing cabling alternatives. These factors relate to the physical attributes of the media, such as strength and shielding. The following are the primary threats related to network cabling:
- Physical damage – Damage can be caused by accident or on purpose.
- Tapping – Physically tapping a device into a network would allow an attacker to perform all sorts of network attacks including sniffing.
- Electromagneticinterference (EMI) – Electrical equipment and cabling near the cable can produce an electromagnetic field that interferes with the signal on copper wires.
- Crosstalk – Electrical signals leaking though the cable shielding or enclosure can interfere with other nearby cables and vice versa.
Coaxial cable is used primarily in the older 10Base2 and 10Base5 Ethernet networks. It is physically strong and rigid and provides relatively good shielding against EMI and crosstalk. One of the main vulnerabilities of using coaxial media is that it is fairly easy to tap in a rogue network device by piercing the cable with a vampire tap or cutting the cable and inserting a T-connector.
Unshielded Twisted Pair (UTP)
The main advantages of Unshielded Twisted Pair (UTP) cabling are that it is cheap and it is flexible. It does however provide very little protection to physical damage and EMI because it does not have proper shielding. It is also fairly easy to tap into an existing connection by splitting the cable wires.
Shielded Twisted Pair (STP)
Shielded Twisted Pair (STP) is a bit more expensive than UTP but has an additional layer of metal shielding enclosing the inner wires. This provides better protection against EMI and makes it physically stronger, while remaining flexible. Tapping into an STP connection is just as easy as with UTP.
The most expensive type of cabling, fiber optics allows for the longest distances and highest transmission speeds, and is also considered the most secure type of network cabling. The two characteristics that make it so secure are that fiber optics is not susceptible to EMI and crosstalk, and it is difficult to physically tap into a connection. A main disadvantage of fiber optic cabling is that it is physically weak, which can pose a threat for the availability of a connection. An attacker may be able to break any cable just as easily, but accidental damage to fiber optics is not uncommon and makes the connection unavailable to everyone.
Not only is today’s remove media able to hold large amounts of data, it is becoming smaller and lighter. This is convenient to the user, but also for fraudulent employees, corporate spies, and thieves. Regardless of the type of media, content encryption provides the best security against theft and loss. If the media itself does not use a file system that supports data encryption, users should use other forms of protection. Third-party encryption products can be used to automatically encrypt and decrypt data on removable media, or at the very least, the data can be places in a password protected ZIP archive.
Removable media such as floppy disks are often a source of virus and spyware because they tend to be swapped between different systems, e.g. at home and at the office. Since networking became available for virtually every computer, support for removable media other than read-only CDs and DVDs is usually no longer required for every client workstation. Just as disabling unnecessary protocols and services on a network server, removable media should not be supported on a user’s computer unless it is necessary for work related tasks. Employees should be made aware of the risks involved in using removable media and the allowed use and transport of removable media should be detailed in an Acceptable Use policy.
Protecting the availability of information is just as important as protecting the confidentiality and integrity. The availability of data on removable media is threatened mostly by physical damage of fire, water, electricity, magnetic fields, and mistreatment. When designing a backup plan, removable media may have to be included to reduce the risk of losing company data.
Since the introduction of flash cards and USB memory sticks, diskettes, or floppy disks, have dramatically decreased in popularity over the past decade. Besides the limited amount of data they can hold, floppy disks are highly vulnerable to damage by magnetic fields and the environment. This makes them unsuitable for storing and archiving data compared to today’s alternative removable media. Another less obvious vulnerability arises when floppy disks are thrown away with the garbage without being properly destroyed. A broken floppy disk may not be readable in a floppy drive but it may still be possible to retrieve information from the disk. That makes floppy disks a valuable find for dumpster divers. The best defense against such malicious activity is to ban floppy disk drives from client systems entirely. This also reduces the risk of employees smuggling confidential information out the company. Floppy disks that are thrown away should be properly destroyed.
CDs and DVDs are currently the most popular removable media and a CD/DVD drive is standard on almost any computer. Many of the new computers are equipped with a CD/DVD-recorder, standard or optional. Unless the user actually needs a recorder to perform job tasks, a client should not be equipped with a CD/DVD-recorder. This reduces the risk of theft of company data and employees using company equipment to create illegal copies of company software or other copyright protected material.
CDs and DVDs are immune to magnetic and static electricity, but should be handled with care. Unlike a floppy disk or tape, the medium is not protected by a cover unless it is stored in its case. A scratch on either side of the disk, direct sun light, or high temperatures can have disastrous results. The file system on CDs does not support data encryption. If CDs are used to store confidential information, the data should be encrypted before it is burned to the media.
Not your typical ‘removable’ media, but swappable and external hard drives have become very popular, especially on servers. Besides easy replacement in case of a disk failure, disks can be stored and transported just a conveniently as regular removable media. Swappable hard drives usually can be locked into a computer; only authorized personnel should have access to the key. This will not protect against a burglar taking the entire system, but will make it more difficult for someone to smuggle the hard drive outside. Just as with other types of removable media, file encryption should be used to protect the data on the hard drive even when it, or the entire system, is stolen.
Although hard drives are usually protected by a strong metal cover and offer some sort of shock resistance, they should be handled with care. Even the best hard drives can fail for no apparent reason. This threatens the availability of the data on the hard drive, so it is important to create regular backups to external media. When a hard drive breaks down, it does not necessarily mean the data is lost. Companies specialized in recovery may be able to retrieve the data from the actual disks, although this is usually an expensive.
For non-IT folks tapes may seem a bit old fashion but tape is still the most popular backup medium. They are fast and can hold the data of many systems in a network combined. Servers are often equipped with tape devices and only designated IT personnel has access to the device and the tapes. Tapes are susceptible to environmental and magnetic damage, but modern tapes are enclosed in a cartridge that protects them from physical damage. In many organizations, backup tapes store all of the essential data that is required to continue operations in case of a disaster. For this reason, tapes are usually stored securely in a safe, which protects it from both threats such as fire, floods, and theft.
Flashcards are becoming very popular because of their small size, large data capacity, and broad application. Mobile devices such as PDAs, digital cameras, smartphones, MP3 players, and other handheld devices, use a variance of flashcards. Even the newer notebooks and desktop computers are equipped with one or more card readers, and external flashcard readers can be attached to USB ports. Many of today’s mobile devices support encryption of data on flashcards, and for computers there are products available that automatically encrypt and decrypt data on flashcards. Because flashcards do not have any mechanical parts, are small, and weight only a couple of grams, they can easily withstand a fall and are shockproof.
As mentioned in the Authentication chapter, smartcards are small intelligent devices usually the size of a credit card, and hold integrated circuits and a microprocessor. The ICs and microprocessor allow the smart card to generate keys, hold a certificate, encrypt information, and perform other complex calculations. Although smart cards usually store small amounts of data, the data is usually sensitive, and can be very valuable to a malicious individual. Smart cards are usually protected by a PIN or pass code, which are fairly difficult to break, but sometimes easy to steal. Just as with passwords, it is important to educate users to use the smartcards responsibly and keep the PIN or passcode confidential.