Section 4.3 Privacy and Security

Websites, apps, and devices can collect data about user activity, including searches, clicks, page views, purchases, and device information. Some systems also collect or infer location and other details based on signals from the device or network.

Collected activity data can be used to personalize experiences, such as search results or recommendations, and may also be used for advertising or analytics, depending on user settings, company practices, and applicable laws.

Cookies are small pieces of data that a website stores in a user’s browser or device to remember information such as login status, preferences, or items in a shopping cart.

Cookies and other identifiers can be used to recognize a user across visits and, in some cases, across different sites or apps, enabling measurement, personalization, and targeted advertising.

Geolocation data estimates or identifies a device’s physical location. It can enable useful services, like navigation or nearby results, but can also reveal sensitive patterns, such as where someone lives, goes to school, works, or spends time.

Data from different sources, such as geolocation, browsing history, app activity, purchases, and social media, can be aggregated to create a detailed profile of an individual. Even if a single data point seems harmless, combining many points can reveal identity, habits, and relationships.

Some data is personally identifiable information (PII). Some PII is directly identifying, like a name or phone number, and some becomes identifying when combined with other data. Examples include: full name, phone number, email address, Social Security number, government ID numbers, precise location, and biometrics.

Privacy risks increase when data is stored, shared, or reused beyond the user’s expectations. Once information is posted or shared digitally, it can be copied, forwarded, or saved by others, making it difficult to fully control or remove.

A data breach occurs when sensitive data is accessed, disclosed, or stolen by an unauthorized party, often because data was stored insecurely, shared improperly, or protected by weak security controls.

When PII is exposed in a data breach, individuals may be at risk of harms such as identity theft, account takeover, or fraud, especially if the data can be used to impersonate them or access their accounts.

Reusing the same password across multiple accounts increases the risk of account compromise because, if one account’s password is exposed, an adversary can try the same username and password on other services to gain unauthorized access.

Social engineering is a strategy adversaries use to compromise systems by targeting people rather than exploiting a technical weakness. An adversary influences a user into taking an action that compromises security, often by impersonating a trusted source or creating urgency, fear, or curiosity.

Phishing is a type of social engineering in which an adversary attempts to influence a user into revealing personal information, such as passwords or verification codes. Adversaries can use that information to access accounts, financial services, or other protected systems.

Unsolicited emails, attachments, links, and forms can be used to gain unauthorized access by influencing a user into opening a file, entering information, or installing harmful software. These messages may come from unknown senders or from accounts that appear familiar because they were compromised.

Malicious links can be disguised to look trustworthy, such as by using misleading text, shortened URLs, or look-alike website addresses, leading users to fake pages or unsafe downloads.

Email is not inherently private. Email messages can be forwarded, stored, intercepted, or accessed by people other than the sender and receiver, which can expose sensitive information if an account or message is accessed by an unauthorized party.

Malware is software designed to harm a device or enable unauthorized access, such as by stealing data, monitoring user activity, or controlling parts of the system. Malware can be installed through unsafe downloads, malicious attachments, or compromised websites.

Adversaries often focus on moments when users are rushed or confused such as with urgent "account locked" messages. These situations increase the chance a user will click a link, share information, or approve access without noticing warning signs.

Authentication is how a system verifies a user’s identity, such as with passwords, passkeys, or biometrics. Strong authentication can reduce unauthorized access to devices and accounts.

Multifactor authentication (MFA) requires two or more different pieces of evidence, typically in at least two of the following categories: knowledge (something a user knows), possession (something a user has), and biometrics (something a user is). MFA adds protection because an attacker must compromise multiple factors, not just a single password, to access an account.

Encryption encodes data so it cannot be read without a key. Decryption decodes it so it can be read. Encryption helps protect data stored on devices and sent over networks.

End-to-end encryption is a method of secure communication in which data are encrypted on the sender’s device and can only be decrypted on the intended recipient’s device, so services that transmit or store the data along the way cannot read the contents without the decryption key.

Systems can be compromised when adversaries exploit software flaws. Installing software updates helps reduce risk by fixing known vulnerabilities that adversaries may target.

Malware scanning tools can help detect or block some malicious software, reducing the chance that a device is infected or controlled without the user’s knowledge.

Apps and websites sometimes request permissions like access to location, contacts, microphone, camera, or photos. Reviewing and limiting permissions helps protect privacy and reduces the chance of misuse if an app is untrustworthy or becomes compromised.

Security measures reduce risk in different ways: authentication and MFA limit who can access an account, encryption limits who can read data if it is intercepted or stolen, updates reduce known weaknesses adversaries exploit, and permissions limit what an app can access. No single measure prevents all compromise, so systems often use multiple protections together.