The most *notorious,* sure. But the most *successful?* Clearly that's unknown.
Yes, ignoring evidence of actual crimes, and focusing on nebulously defined threats with vague insinuations is what discrimination is.
If the best the PRC can manage after literal decades of unfettered access to the deepest, darkest secrets of the United States, such as single crystal blade growth techniques, submarine diesel generator rafting, and nuclear warhead design is to desperately beg Curtiss-Wright to fix their broken reactor pumps, spend a decade reinventing Pershing II with a full TDP, and squeak out the latest and greatest jet engine of 1975 after 30 years of copying America's homework on F119 and F135, I'd say we're pretty safe to continue hiring Chinese/Korean/Iranian/whatever for government programs.
Just watch out for dudes from Florida or New Jersey who change cars often. Perhaps the FBI should consider opening a used car dealership hotline as a nexus for knowledge on foreign leaning spies. "I will pay for your new cars/house/golf clubs with cash," is a pretty strong motivator for the typical native-born American, but much less so for highly skilled foreign immigrants, to a shockingly large degree.
The worst spies, in terms of damages to American national security and lack of moral scruples, are invariably going to be native-born Americans who feel like they aren't getting their just deserts: not only are they lacking that baseline level of discrimination aimed at foreigners but they're also in position to actually feel entitled, rather than indebted, towards American society. This means they get put in positions where poor handling of sensitive information is less likely to be scrutinized and more likely to share that with randoms anyway. So what country was Jack Teixeira from again?
The foreign students from PRC that actually don't like America are generally loud enough to be heard through ten feet of air-gapped concrete and oak safety doors in the dorm commons room, mostly spend their time playing MMORPGs instead of studying, and are getting all-expenses paid by their rich parents to stay at an engineering university in the American Midwest in a small suburban-rural factory town. All solely so they can check that box off their CV and get a cushy do-nothing government job in downtown Shanghai or Shenzen. Hardly a security risk, considering they barely go to their classes and have no desire to stay in America, since they usually find four to five years for a degree to be long enough.
OTOH, when one of the Chinese restaurants closed near my school, the joke was that the owner was a spy and she got sent home by DHS.