Durham had approximately 1 month and 11 days to secretly work as a special counsel before it was officially announced

According to 28 C.F.R § 600.9(a)(1) Chairman and Ranking Minority Member of the Judiciary Committees of each House of Congress have to be notified upon AG appointing special counsel. However AG can delay this if there are privacy concerns or other legitimate reasons and this is what AG Barr did. So Durham has been working as special counsel since 19th of October and MSM first caught up on it around 1st of December, meaning Barr likely lifted the delay and notified appropriate parties and it soon leaked to the media from there. For around 1 month and 11 days Durham had time to secretly investigate people and he likely accomplished all his main goals as the delay was lifted.

Q even teased the DS on this. His "Durham" post on Friday the 13th was funnily enough posted on what we know as "unlucky day" and unlucky it is indeed for them.

Furthermore 28 C.F.R § 600.8(c) says Special Counsel's final report to AG will be confidential and this report includes who will be prosecuted amongst other info. Now comes the good part for us: AG Barr asks Durham to provide additional final report and possible interim reports which are prepared in a way that they can be shown to the public. So we all get maximum transparency on Durham's entire investigation.

https://www.law.cornell.edu/cfr/text/28/600.8

https://www.law.cornell.edu/cfr/text/28/600.9

https://www.politico.com/f/?id=00000176-2008-d692-a977-3c7afcd50000