A drive-by download is the installation of unwanted software, or the start of an infection, that happens when a person simply visits a web page, without knowingly clicking a download button. It usually relies on a flaw in the browser, a plugin or the operating system.
Why it matters
Visitors do nothing wrong beyond loading a page, and the page may belong to a trusted site that was compromised or that loaded a malicious advertisement. For site owners, a compromised site can harm visitors, trigger browser warnings, and damage search visibility and reputation.
Example
A small business site is hacked, and a hidden script is added that loads code from another domain. Visitors with outdated browsers are redirected through a chain of pages that tries a known flaw. Keeping browsers updated, limiting third-party scripts with a Content Security Policy and monitoring file changes lowers both the chance and the impact.
Common mistakes
- Delaying browser and operating system updates.
- Loading third-party scripts and ads without review.
- Not monitoring the site for unexpected file or script changes.
- Assuming a well-known site cannot serve harmful content.
Related
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This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.