China has routinely denied hacking into businesses or governments in other countries. State-sponsored hackers from China have developed techniques that evade common cybersecurity tools and enable them to burrow into government and business networks and spy on victims for years without detection, researchers with Alphabet Inc.’s Google found. Over the past year, analysts at Google’s Mandiant division have discovered hacks of systems that aren’t typically the targets of cyber espionage. Instead of infiltrating systems behind the corporate firewall, they are compromising devices on the edge of the network—sometimes firewalls themselves—and targeting software built by companies such as VMware Inc. or Citrix Systems Inc. These products run on computers that don’t typically include antivirus or endpoint detection software.

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