Alexander wanted to use the NSA’s powerful tools to scan Internet traffic for malicious software code. He said the NSA could kill the viruses and other digital threats without reading consumers’ private emails, texts and Web searches.

The NSA normally protects military and other national security computer networks. Alexander also wanted authority to prevent hackers from penetrating U.S. banks, defense industries, telecommunications systems and other institutions to crash their networks or to steal intellectual property worth billions of dollars.

But after Snowden, a contractor, began leaking NSA systems for spying in cyberspace that went public in June, Alexander’s proposal was a political nonstarter, felled by distrust of his agency’s fearsome surveillance powers in the seesawing national debate over privacy and national security.

It was one of several Obama administration initiatives, in Congress and in diplomacy, that experts say have been stopped cold or set back by the Snowden affair. As a result, U.S. officials have struggled to respond to the daily onslaught of attacks from Russia, China and elsewhere, a vulnerability that U.S. intelligence agencies now rank as a greater threat to national security than terrorism.

More: Several Cyber Security Initiatives Lost After Snowden’s NSA Leaks