The threat here is that networking hardware made by Chinese companies such as Huawei and ZTE, or counterfeit hardware made in China or elsewhere, may contain malicious hardware or firmware code, which provides a backdoor into corporate systems. This has always been a possibility, but in October 2012, the House Select Committee on Intelligence explicitly recommended that private sector entities consider "the long-term security risks associated with doing business with either ZTE or Huawei for equipment or services."
What you can do to mitigate the threat: At the very least, limit networking hardware purchases to trusted vendors. Additional measures include carrying out network listening to detect hardware acting maliciously, and carrying out random tests on devices to look for indications that they contain extra components or malicious firmware. At the highest level, some companies may choose to assume that all hardware is compromised and continuously monitor it for unexpected behavior.
The security threat landscape changes constantly, with malicious hackers developing new ways to compromise your systems as older vulnerabilities are discovered and patched. So it's important to be aware of the threats to enterprise security that are coming over the horizon and heading this way.