It took 8.8 days, on average, for threats to become known by hash to antivirus engines ‘ giving hackers over a week’s ‘head-start’ to further their campaigns. 29% of malware captured was previously unknown ‘ due to the widespread use of packers and obfuscation techniques by attackers seeking to evade detection. The most effective execution techniques we saw in Q4 2020 involved old technologies like Excel 4.0 macros that often offer little visibility to detection tools.
Source: https://www.helpnetsecurity.com/2021/03/18/flaws-exploited-deliver-malware/