CS345 Study Materials: Intro to Information Security & Command Line Skills Flashcards

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CIA triad

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Confidentiality, Integrity, and Availability are core security goals used to reason about protection needs. They are important but do not fully encompass the breadth of computing in the presence of adversaries.

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Adversarial computing

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Computing in the presence of adversaries means designing and operating systems assuming hostile actors will try to exploit weaknesses. This perspective expands beyond CIA to include social, physical, and embedded attack surfaces.

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National Vulnerability Database

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The NVD catalogs known software vulnerabilities and their metadata, and shows large yearly counts of reported issues (tens of thousands per year). It demonstrates the scale and continual growth of discovered flaws.

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Common attack types

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Attacks include social engineering, man-in-the-middle, and distributed denial-of-service among many others. Defenders must consider how attacks work, what they target, and possible mitigations across varied domains.

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Embedded systems

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Embedded systems run specialized software on devices like thermostats or cameras and may lack typical protections. Even non-networked devices can be denied service or abused through software bugs or physical interactions.

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IP address format

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An IPv4 address is commonly written as A.B.C.D with each of the four octets between 0 and 255. In many contexts, an IP address serves as a practical unique name for a host.

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Bit and byte

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A bit is a binary value 0 or 1; eight bits form a byte. All digital data is ultimately represented as sequences of bits and bytes, and higher-level meaning is assigned by software.

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Nibble

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A nibble is 4 bits, half of a byte, and conveniently maps to a single hexadecimal digit. It is useful for grouping bits when converting between binary and hex.

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Byte as number

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A single byte interpreted as an unsigned integer ranges from 0 to 255 using base-2 positional weights. Multi-byte sequences combine bytes to represent larger integers using agreed conventions.

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Hex and octal

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Hex (base 16) and octal (base 8) are compact human-friendly ways to write binary, grouping bits into 4 (hex) or 3 (octal). Programming literals often use prefixes like 0x for hex and a leading 0 for octal.

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ASCII

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ASCII is a 7-bit character encoding mapping values 0–127 to control and printable characters. Extended 8-bit encodings and Unicode address multilingual needs, but 7-bit ASCII remains the core for control vs printable separation.

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Everything is a file

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In Unix-like systems most resources are represented as files: regular files, directories, devices, and sockets. This unifying model makes tools and permissions apply consistently across many resource types.

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Absolute vs relative paths

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An absolute path starts at the root '/' and names a file regardless of current directory; a relative path is interpreted from the current working directory. Use absolute paths for fixed references and relative paths for local navigation.

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Working directory

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The current working directory is where command-line commands operate by default; use pwd to print it and cd to change it. Many relative path operations depend on the working directory.

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File meta-data

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Files have metadata such as owner, group, size, times, and permissions that are distinct from their byte contents. This information affects access control and auditing.

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Unix permissions

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Unix permissions separate access into owner, group, and world with read, write, and execute bits for each. chmod sets these bits often using octal notation like chmod 754 to specify owner/group/world modes.

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Basic file commands

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Core command-line operations include ls for listing, cat for printing files, cp for copying, rm and rm -r for removal, and mkdir/rmdir for directories. Text editors like nano and vi let you create or edit files on the command line.