What is process-level site isolation and how does it prevent cross-site attacks?

Modern web browsers have come a long way from the simple architecture where every tab ran within a single shared process. Today, developers use advanced isolation technologies where each site or even individual iframe elements open in strictly isolated system processes with limited access rights.

The main goal of this approach is to prevent situations where a vulnerability in one web application allows attackers to gain control over neighboring tabs or the entire operating system. If a malicious script on one site attempts to exploit a memory vulnerability, its capabilities will be strictly limited to the scope of that specific system process.

Site isolation technology also plays a key role in protecting against hardware-based side-channel attacks such as Spectre and Meltdown. These attacks allow malicious code to read the memory contents of other processes at the CPU level. Separating data from different sites into separate processes makes gathering confidential information significantly more difficult.

Users rarely need to configure this feature manually, as it is enabled by default in most modern browsers. However, developers and system administrators can check the isolation status through the browser's built-in task managers to ensure that processes are distributed correctly.

Understanding the principles of process isolation helps to better assess software stability and security. If one tab freezes or crashes, the isolated architecture prevents the entire browser from crashing, preserving unsaved data in neighboring workspaces.