What is the term for an attack that uses techniques that anti-virus does not yet detect?

The term for an attack that utilizes techniques not yet recognized by antivirus solutions is referred to as zero-day threats. This designation applies to vulnerabilities that are exploited by attackers before the software vendor is aware of them and before any patches or updates have been implemented. Essentially, these attacks take advantage of the "zero-day" period, meaning there are zero days of awareness by the security providers about the vulnerability, making it particularly dangerous since traditional antivirus solutions and other security measures may not be effective against it.

In contrast, the other types of attacks listed have different characteristics. Phishing attacks involve tricking individuals into revealing sensitive information through deceptive emails or websites, rather than exploiting unknown system vulnerabilities. Ransomware is a category of malware that encrypts users' files and demands a ransom for decryption, but it typically targets known vulnerabilities rather than zero-day exploits. Social engineering encompasses a wide range of tactics that manipulate individuals into breaking security protocols, again focused more on human factors rather than exploiting unrecognized software vulnerabilities.