What Security & Verification Basics covers
This section covers the underlying vocabulary of online security and identity: what social data is and how it is used, what an IMEI number does, what the dark web actually refers to, and similar terms encountered without explanation.
These are the concepts that make everything else make sense. A great deal of security advice assumes you already know what identifies you online, what a device identifier is, or what is meant when a news report says data appeared on the dark web. The guides here fill that in without assuming a technical background.
Two terms are worth setting straight immediately because they are so commonly misunderstood.
The dark web is not a secret criminal internet. It is a portion of the web reachable only through specific software, most commonly Tor, which routes traffic through several relays to obscure its origin. That anonymity is used by criminals, and it is also used by journalists, activists and people under surveillance. When a breach notification says your details were found on the dark web, it means they appeared on a marketplace or forum there — the actionable part is that a service holding your data was breached, not the location.
An IMEI number is the unique identifier of a mobile handset itself, separate from the SIM and the phone number. It matters because it identifies the physical device: reported stolen, it can be blocked across networks so the handset is unusable even with a new SIM.
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Most searched questions in this topic
How the guides in this section differ
Identifier or concept. Some entries are things that identify you or your device — an IMEI, an account, a phone number. Others are concepts describing how parts of the internet work.
About you or about your device. A phone number and an account identify a person. An IMEI identifies hardware. That distinction matters when something is stolen, because different remedies apply.
Data you gave or data inferred. Social data covers both what you actively posted and what platforms derive from your behaviour. The second category is larger than most people expect and is generally what advertising is built on.
| Term | What it identifies or describes | Why it matters to you |
|---|---|---|
| IMEI | The handset itself | Can be blocked if the phone is stolen |
| Phone number | A line, transferable between SIMs | Why SIM swap works |
| Social data | Posted and inferred behavioural data | What targeting and profiling use |
| Dark web | Web reachable only via anonymising software | Where breached data often surfaces |
Related topics and alternatives
- Explore CAPTCHA, Bot Checks & Human Verification
- Explore OTP, 2FA & Authentication Codes
- Explore Security, Privacy & Access Tools
Safety, accuracy and next-step checks
These guides follow reputable cyber-safety and service-provider guidance.
Points worth carrying:
- Record your IMEI now, before you need it. Dial
*#06#on the handset to display it, and keep it somewhere separate from the phone. Without it, blocking a stolen handset is far harder. - Report a stolen phone to your network and to the police. The network can block the IMEI; the police report is generally needed for insurance.
- Do not pay anyone offering to “remove your data from the dark web”. Once data has been copied and traded it cannot be recalled. Services promising removal are selling something they cannot deliver.
- Act on the breach rather than the location. If your details appeared in a breach, change that password, change it anywhere you reused it, and enable two-factor authentication.
- Use a password manager and stop reusing passwords. Credential stuffing — trying breached username and password pairs against other sites — works only because reuse is common.
- Review what you publish. Birthdays, pet names, school names and family details are the raw material for both security questions and convincing impersonation.
- You have rights over your personal information. Under POPIA you can ask an organisation what it holds about you and request correction.
- Never share codes, PINs or passwords with anyone, regardless of who they claim to be.
Frequently asked questions
What is an IMEI number used for? It uniquely identifies a mobile handset. Its practical value is that a stolen phone can be blocked by IMEI so it cannot be used on networks even with a different SIM.
How do I find my IMEI? Dial *#06# and it appears on screen. It is also printed on the original box and in the phone’s settings.
Is the dark web illegal? The technology is not illegal, and it has legitimate uses in journalism and human rights work. Some activity conducted there is criminal, as it is on the ordinary web.
My data was found on the dark web. What should I do? Change the password for the affected service and anywhere you reused it, and turn on two-factor authentication. Ignore anyone offering paid removal — it is not possible.
What is social data used for? Advertising targeting, personalisation and profiling. It includes both what you post and what is inferred from how you behave.