So....”it was like this when I got here”??!
My point about the Dominion war was not made in vain.Real world this for a minute.
If Starfleet hadn’t done a root and branch review of security measures during and in the wake of a war against a shapeshifting enemy then that is incredible incompetence.Incredible as in not credible.
DS9 made it pretty clear that Starfleet did an extensive root-and-branch review of security measures in the years leading up to the Dominion War.
Nedar was just
that good.
But blood tests would do dick all to help against Romulan infiltrators, whom had been de facto allies for a time in the Dominion War. So, this idea that somehow they could runaround on a flushing mission would turn in to the very witch hunt Admiral Sati was accused of doing, and potentially ruined the lives of other officers in the process. In addition, as noted above, the Romulans are extremely good at this infiltration business, as evidenced by the Vulcan ambassador who was in deep cover for a time. So, Vulcan's security measures are apparently extremely poor too.
Pedantic side note: I'm pretty sure Selok's identity as T'Pel of Vulcan was supposed to be an ambassador of the UFP who was Vulcan rather than an ambassador of the Vulcan polity. In that instance, she would have been subject to Federation security measures, not Vulcan security measures.
SI is an intelligence organisation (allegedly).The degree to which they are comprised is ridiculous.
I dunno. It doesn't look implausible to me, given the degree to which real-life intelligence agencies leak and get compromised. I mean,
Hell -- how many times did Kim Philby come under suspicion before MI6 was finally like, "Oh, hey, I think this man is a Soviet agent!" ?
So less George Smiley and more George Costanza.

Hopefully 31 gets all the smart ones.
I doubt it. Canonically, we have seen Section 31 undertake eight operations, and six of them have had
disastrous unintended consequences:
- Their decision to allow Klingon agents to abduct Phlox from Earth in order to coerce him into assisting in curing the Augment virus in 2154 directly led to the greater Klingon hostility towards the Federation in the 23rd Century, as Klingons viewed the subsequent mutations the virus produced as a threat to their purity created by the Federation (ENT: "Affliction/Divergence," DIS: "The Vulcan Hello"/"Battle at the Binary Stars") This led to the Federation/Klingon War of 2256-2257 that nearly led to the collapse of the Federation and conquest of Earth (DIS: "Will You Take My Hand?")
- Their attempt to use the artificial intelligence known as Control to automate a vast number of command decisions across Starfleet in 2257 instead led to Control going rogue, the murders of almost all Section 31 personnel at their headquarters, and the attempted extermination of all life in the Milky Way Galaxy (DIS: "Project Daedalus," "Such Sweet Sorrow," et al S2)
- In 2259 of the Kelvin Timeline, their attempt to use the recovered Augment known as Khan Noonien Sign to provoke a war with the Klingon Empire (which they could use as a pretext to overthrow the Federation government) led instead to Khan's bombing the Kelvin Memorial Archive and then crashing the Section 31 ship USS Vengeance into downtown San Francisco, likely killing thousands of innocent Federation civilians (Star Trek Into Darkness)
- Their attempt to kidnap and indoctrinate Julian Bashir into joining their organization in 2374 failed utterly and instead led him to start opposing them at every turn (DS9: "Inquisition")
- Their attempt to overthrow Senator Cretek and install their mole Tal Shiar Chair Koval onto the Continuing Committee was initially successful in 2375, but Koval was a subsequent failure -- he failed to predict or impede the rise of Shinzon, and then in 2379 he failed to prevent Shinzon's agent Tal'Aura from assassinating the entire Romulan Senate, he failed to prevent Shinzon from seizing power as Praetor, and he failed to prevent Shinzon from threatening the Federation (DS9: "Inter Arma Enim Silent Leges;" NEM)
- Their attempt to infect the Great Link with the changeling virus only prompted the Female Shapeshifter to order outnumbered and outgunned Dominion forces in orbit of Cardassia to give the Allies a Pyrrhic victory after Dominion forces had been defeated by conventional means. A horrific bloodbath was only averted when Odo agreed to give the Founders the cure (DS9: "Extreme Measures," "The Dogs of War," "What You Leave Behind")
- Their genocide attempt also provoked the Female Shapeshifter into ordering the attempted extermination of the Cardassian species in the final hours of the war, leading to hundreds of millions of deaths at minimum ("What You Leave Behind")
Literally the only successful Section 31 operations we have seen that did not have dire unintended consequences were the decision to give the
Enterprise NX-01 team the info they needed to defeat Terra Prime on Mars (ENT: "Terra Prime") and Mirror-Phillipa's mission to protect Chancellor L'Rell from rivals for the Klingon throne (DIS: "Point of Light").
That's a really bad track record. Section 31 are
not the brightest bulbs on the Christmas tree.