Step 1: Recall the base law.
The Information Technology Act, 2000 is India's core cyber law dealing with digital signatures, cybercrime and electronic governance.
Step 2: Recall its major amendment.
The IT Act was substantially amended through the Information Technology (Amendment) Act, 2008, which strengthened cybercrime provisions.
Step 3: Eliminate the other years.
2021 relates to separate IT Rules rather than an amendment to the Act itself, and 2010 and 2025 are not recognised amendment years for this Act.
\[ \boxed{\text{2008}} \]