Katarina Armstrong, aka Spy Smasher, is an agent with U.S. Intelligence.
Which agency, you ask? Apparently, all of them. She has valid credentials for virtually every one of the government's alphabet soup members. FBI, DOD, CIA, BAT, etc. She also has membership rights to the U.K.'s MI-6. And she is a proud member of Checkmate, which in the DC Comics universe is a major player in fighting international terrorism as well as out-of-control meta-humans.
How she got her codename of Spy Smasher and what her background is remains a mystery but it is not a far stretch to believe she inherited the right to the name as her last name, Armstrong, would make her likely the granddaughter of the original Spy Smasher, Alan Armstrong, likely the product of the product of his and Eve Corby's marriage. If so, she inherited more than just his name but also his good lucks, blond hair, and his incredible athleticism and marksmanship.
There are important differences between this Spy Smasher and the original. Whereas the first one was a solo act, never getting involved with any group and preferring to go it alone and unauthorized, the second one is more of a team player. Well, as long as she is allowed to lead the team. Following is not something she does, ah, ever.
When Katarina Armstrong walks into a room, she owns it. She would not have it any other way. She is not friendly about it. She is not particularly loud about it. It is a fact and she knows it and she makes sure everyone else there knows it as well. And if someone has the temerity to challenge her, she has the skill set to back up her chutzpah and enough enjoyment of the rough stuff that it is also a pleasure. Impressive lady. Spooky, but impressive.
During the times she has been active, she has worked with the Birds of Prey group led by Oracle (formerly Batgirl), Checkmate, and the Secret Six. She has come up against Dick Grayson (formerly Robin and Nightwing) while he was a covert agent. She has definitely gotten around. Sometimes she loses and sometimes she is tied but usually she comes out on top and when she doesn't, it is seldom nice for those around her.
Armstrong certainly lives up to her codename of "smasher".