What is multitasking? It is the simultaneous execution of more than one application on a computer and is managed by the operating system.
What is multithreading? Multithreading permits multiple concurrent tasks to be performed within a single process.
Multiprocessing? It is the use of more than one processor to increase computing power.
Multiprogramming? It is similar to programming but takes place on mainframe systems and requires specific programming.
Single State Processors are capable of operating at only one security level at a time. Multistate processors can simultaneously operate at multiple security levels.
Four security modes approved by the federal government for processing information are:
Dedicated systems require that all users have appropriate clearance, access permissions, and need to know for all information stored on a system.
System high mode removes the need-to-know requirement and the access permission requirement. Multilevel mode removes all three requirements.
Two layered operating modes used by most modern processors:
User applications operate in a limited instruction set environment known as user mode. the operating system performs controlled operations in privilged mode, also known as system mode, kernel mode, and supervisory mode.
Types of memory in a computer:
ROM, nonvolatile and can’t be written to by the user
PROM, can be written to by the user
EPROM may be erased using ultraviolet light and then can have new data written.
EEPROM can be erased with electrical current and then have new data written on them.
RAM are volatile and lose their contents when the computer is off.
Security issues surrounding memory components:
3 main security issues:
Data may remain on the chip after power is removed.
Memory chips is highly pilferable
Control of access to memory in a multiuser system.
Describe the different characteristics of storage devices used by computers.
Primary storage is the same as memory
Secondary storage consists of magnetic and optical media that must be first read into primary memory before the CPU can use the data.
Random access storage devices can be read at any point, whereas sequential access devices require scanning through all the data physically stored before the desired location.
There are three main security issues surrounding secondary storage devices: removable media can be used to steal data, access controls must be applied to protect data, and data can remain in media after file deletion or media formatting.
Understand security risks that input and output devices can pose.
They are subject to eavesdropping and tapping, used to smuggle data out of an organization or used to create unauthorized, insecure points of entry into an organization’s system and networks. be prepared to recognize and mitigate such vulnerabilities.
Working with legacy PC devices requires some understanding or IRQs, DMA, and memory-mapped I/O. Be prepared to recognize and work around potential address conflicts and misconfigurations and to integrate legacy devices with Plug and Play counterparts.
Firmware is the software stored on a ROM chip. At the computer level, it contains the basic instructions to start a computer. Firmware is used to provide operating instructions in peripheral devices such as printers.
Process isolation ensures that individual processes can access only their own data.
Layering creates different realms of security within a process and limits communication between them.
Abstraction creates “black-box” interfaces for programmers to use without requiring knowledge of an algorithm’s or device’s inner workings.
Data hiding prevents information from being read from a different security level
Hardware segmentation enforces process isolation and physical controls.
The role of a security policy is to inform and guide the design, development, implementation, testing, and maintenance of some particular system.
Cloud computing is a popular term referring to a concept of computing where processing and storage are performed elsewhere over a network connection rather than locally.
AKA Internet-based computing.
Least privilege ensures that only a minimum number of processes are authorized to run in supervisory mode.
Separation of privilege increases the granularity of secure operations. Accountability ensures that an audit trail exists to trace operations back to their source.
Avoiding single points of failure includes incorporating fault-tolerant systems and solutions into an environment’s design. Fault tolerant systems include redundant or mirrored systems, TFTP servers, and RAID. You should also address power issues and maintain a backup solution.
A covert channel is any method that is used to pass information but that is not normally used for information.
A buffer overflow occurs when the programmer fails to check the size of input data prior to writing the data into a specific memory location. In fact, any failure to validate input data could result in a security violation.
In addition to buffer overflows, programmers can leave back doors and privileged programs on a system after it is deployed. Even well-written systems can be susceptible to time-of-check-to-time-of-use (TOCTTOU) attacks. Any state change could be a potential window of opportunity for an attacker to compromise a system.
