President Joe Biden is meeting Wednesday with top executives from some of the country’s leading technology companies and financial institutions as the White House urges the private sector to help toughen cybersecurity defenses against increasingly sophisticated attacks. The summit comes during a relentless stretch of ransomware attacks that have targeted critical infrastructure, in some cases extorting multi-million-dollar payments from major corporations, as well as other illicit cyber operations that U.S. authorities have linked to foreign hackers. Though ransomware is one focus of Wednesday’s gathering, the purpose of the meeting is broader and centered on identifying the “root causes of malicious cyber activities” and ways in which the private sector can help bolster cybersecurity, said a senior administration official who briefed reporters about the gathering on the condition of anonymity. Speaking at the White House, Biden said his administration launched a 100-day initiative to improve cyber security across the electric sector. …