In regulatory and banking circles, there’s growing concern that the bank rot could reach some of the largest privately owned banks, many of which continue to be hobbled by bad loans and inadequate capital. Publicly, Nabiullina and other officials say they don’t see risks of widening problems. The central bank has created a special category for the biggest state and private-sector banks, designating them “systemically significant” and subjecting them to tighter regulation because any shocks could affect the entire financial system. But what’s especially worrisome for Nabiullina and the central bank is how many struggling banks have been able to hide the scale of their financial woes. The full picture only becomes clear when they’re shut down and regulators have to track the assets. In those cases, only about 40 percent of what the banks claimed was on their books actually existed, according to the central bank. There’s no way for regulators to know for sure how much of what’s on the balance sheets of solvent banks is, in fact, real.