Microsoft has announced the phased discontinuation of the RC4 encryption cipher, with full implementation expected by mid-2026. RC4, created in 1987, has been increasingly recognized as a vulnerability, exploited in various high-profile cyberattacks. Microsoft plans to disable RC4 by default in Windows Kerberos authentication, encouraging organizations to transition to more secure alternatives like AES-256. This decision follows years of warnings from the cybersecurity community and aims to eliminate long-standing cryptographic weaknesses. The transition will require organizations to audit and upgrade their infrastructures, as many legacy applications still depend on RC4. Disabling RC4 is expected to reduce the success rates of attacks exploiting weak encryption. Microsoft has introduced tools to help administrators identify hidden RC4 usage. The change reflects a commitment to zero-trust architectures and aligns with recommendations from organizations like NIST. Experts recommend a multi-step approach for organizations to navigate this transition effectively.