Modems provide a bridge between the analog and digital worlds, offering digital systems the ability to communicate over older transmission technologies. Learn about the types of modems that are used in different environments and the security considerations surrounding the use of these devices.
- [Instructor] Modems provide a bridge between the analog and digital worlds offering digital systems the ability to communicate over older analog transmission technologies. The word modem is an abbreviated form of two words that describe the functions that a modem performs. Modulator and demodulator. A modem converts a signal from digital form to an analog form such as audio, electrical impulses, or whatever is required by the transmission media.
This is called modulation. On the other end of the connection a modem converts that analog transmission back to digital form, a process called demodulation. The earliest modems were used to connect computers to telephone lines that were designed to carry audio signals. The device shown here, known as acoustic coupler, converted signals from a computer to sound, literally allowing computers to speak to each other over telephone lines. This technology quickly matured a little bit, getting rid of the need to attach a telephone handset to a computer, and allowing users to directly plug telephone cables into modems.
However, this approach still relied on converting signals to sound and then transmitting them over telephone lines. Today many of use use cellular modems that either plug in to our devices, or are built into them to carry data signals over cellular networks. In home and small office environments digital subscriber line, or DSL communications, use modems to carry high-speed internet over telephone lines, and cable modems perform a similar task to allow the use of cable television infrastructure for data signals.
From a security perspective anyone using modems should carefully understand how they work. In most cases you'll want to figure the modem connection to block any unsolicited inbound requests. In the case of cable or DSL modems this usually means putting a firewall between the modem and the protected network. If you're still using dial-up modems for inbound connections, two more pieces of advice. First, you really should find a way to leverage more modern technology. Second, you must have strong authentication on your inbound connections to prevent attackers from using the modem as an access point into your network.
Learn about communication and networking best practices, including TCP/IP networking, network security devices, and secure network design and management. Instructor and cybersecurity expert Mike Chapple also includes coverage of converged protocols, network encryption, and wireless networking. You can find Mike's companion study books for this series at the Sybex test prep site and review the complete CISSP Body of Knowledge at https://www.isc2.org/cissp-domains/default.aspx.
- IP addressing
- Switches and routers
- Content distribution networks
- Designing secure networks
- Specialized networking
- Managing secure networks
- Working with virtualized networks like SDNs
- Detecting and preventing network attaches
- Transport encryption
- Wireless networking
- Host security
Skill Level Advanced
CISSP Cert Prep: 2 Asset Securitywith Mike Chapple58m 11s Advanced
1. TCP/IP Networking
2. Network Security Devices
3. Designing Secure Networks
4. Specialized Networking
5. Secure Network Management
6. Virtualized Networks
Port isolation1m 47s
7. Network Attacks
8. Transport Encryption
9. Wireless Networking
10. Host Security
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