Yet, especially in the 20th Century, the exploits of heroic undercover Christians and Jews have been an integral part of God's work in the world. For example, the wealthy businessman Oskar Schindler, whose life was portrayed in the film Schindler's List, joined the Nazi Party, engaged in armaments manufacturing, and contrived to rescue at least 1,200 Jews from slavery and death camps toward the end of WWII. Moreover, he lived to tell about it and was declared a member of the 'Righteous Among the Nations' by the Israelis, not only for rescuing victims and getting them out of Germany, but by spending his entire personal fortune (around $7,000,000 in today's dollars) feeding and housing them.
Then there was the Swedish diplomat Raoul Wallenberg, who rescued tens of thousands of Jews from the Holocaust in occupied Hungary; who was arrested by the communists and killed in a Soviet death camp, probably in 1947. (Link)
The Bible is filled with stories of undercover angels - either from God or Satan - who intervene in world affairs; rescuing us from the clutches of death or causing it. (Link) It's a real test of faith for us to maintain our sanity when facing this truth of the global arena, rather like an athlete going from a small town community college into the pro ranks. "Welcome to the NFL" is a saying often heard when a rookie football player gets his first real hit on the gridiron.
Conditions have certainly changed since the New Testament was penned. These days, vocal Christians of every conceivable denomination are everywhere in the media, churches, and streets, proselytizing and persuading. There's little persecution of religious people, relatively. Martyrdom in all its forms - physical and otherwise - is not very common in the western world; unlike early Christian times (though antisemitism is on the rise, certainly). There isn't a need for many more theatrical believers.
So, to be effective at doing God's work, going undercover is clearly a viable and important option; particularly if one works in law enforcement. Exposing sexual abuse, pedophiles, and breaking up international victim importation rings rank high on the list of great and good deeds. But what if working for the police isn't compatible with your abilities and talents? Is there another option? There is, and Oskar Schindler showed the way. One can do God's work in secret, and have an effect, at least for while.
But first, we must be aware of the danger of lying to ourselves about our motives and methods of operation. Self-deception is the gravest danger we face, and it's a whole life's work to eliminate lying entirely. We never can be utterly truthful all the time, because, for one thing, we don't know, and never really can know pure truth in this life. But we don't have to. It's quite enough to honor and conform to the Ten Commandments and the wisdom of Judeo-Christian Scripture. If you are sincere, and seek God on a daily basis, you will be guided and encouraged. If you find this feeling absent, you're much better off doing something else in life. The penalty for joining the wrong side in this ancient Crusade is too terrible to contemplate. The reward for doing it well, however, is unutterably sublime and noble.
Eventually, though, you will be discovered. Even the greatest spies and double agents who ever lived were exposed (James Bond, too, in every film). Many were imprisoned and killed. Some escaped to their home countries. The infamous Klaus Fuchs, a physicist who helped the U.S. build the first nuclear bombs, also passed the information on to Soviet agents in the mid 1940's, which enabled the mass killer Stalin to acquire them. Fuchs was caught and sentenced to fourteen years imprisonment. (Link)
We who stand with God in these Last Days of Tribulation have an awesome choice to make. Will we risk everything we have to help our fellow men and women? Our reward will be indescribably wonderful. It's entirely your choice.