Problems arising from flawed systems, increasingly complex networks and even technology headaches from corporate mergers can make computer systems less reliable.

Meanwhile, society as a whole is growing ever more dependent on computers and computer networks, as automated controls become the norm for air traffic, pipelines, dams, the electrical grid and more.

“We don’t need hackers to break the systems because they’re falling apart by themselves,” said Peter G. Neumann, an expert in computing risks and principal scientist at SRI International.

The best answer, Dr. Neumann says, is to build computers that are secure and stable from the start. A system with fewer flaws also deters hackers, he said.