U.S. officials believe two additional fake videos now circulating online, which the FBI has identified as attempts to spread false claims about election security, are likely part of a Russian-backed influence campaign. The campaign appears to be aimed at swaying public opinion ahead of the Nov. 5 presidential election, two sources familiar with the situation told CBS News. U.S. intelligence agencies and Microsoft have recently warned that foreign adversaries are engaging in influence campaigns to mislead voters ahead of the 2024 election. Both the U.S. government and Microsoft have indicated t…