On behalf of the Russian government, Kaspersky may have altered its own antivirus software in order to steal secrets from the US' NSA. According to The Wall Street Journal, the software was modified to look for documents with labels like "top secret," whereas it would typically just scan for malicious software.
Unnamed US officials told the WSJ that this kind of modification could have only been possible with Kaspersky's knowledge. They say the software also looked for classified code names associated with important US government programs.
Kaspersky has denied any involvement with this sort of software modification.