GCHQ's cyber security advice group has formally warned of the risk of using ZTE equipment and services for the UK's telco infrastructure.

The National Cyber Security Centre, the cyber part of the UK's nerve centre, founded in 2016, has written to UK telecoms companies warning that using gear from the Chinese firm "would present risk to UK national security that could not be mitigated effectively or practicably".

In a statement, the British spooky agency confirmed the veracity of an FT report, but declined to elaborate on what specific vulnerability or threat had prompted the assessment:

"NCSC assess[es] that the national security risks arising from the use of ZTE equipment or services within the context of the existing UK telecommunications infrastructure cannot be mitigated," the agency told us in a statement.

Both Huawei and ZTE have been singled out by US spooks and Congress-critters as posing a potential threat. Unlike privately owned Huawei, with its roots in the bustling Hong Kong trading area, ZTE is a state-owned enterprise, and that's something the NCSC has pointed out.

However Huawei worked hard to address concerns, establishing a centre in Banbury, close to GCHQ, Huawei Cyber Security Evaluation Centre, nicknamed "the Cell". This allowed spooks to examine Huawaei's wares, including its source code. After initial issues about oversight, officials declared the Cell a success.

"HCSEC fulfilled its obligations in respect of the provision of assurance that any risks to UK national security from Huawei’s involvement in the UK’s critical networks have been sufficiently mitigated," the third annual report by the centre's Oversight Board noted last year. HCSEC demands the full source code to Huawei's products so it can rebuild the binaries and replicate their functionality. This isn't always easy, the report noted, due to "complex and subtle technical issues".

No backdoor has ever been found in any Huawei phone, but in 2012 one was found in a ZTE phones.

Last March we exclusively revealed that ZTE's Tier 2 visa licence had been suspended by the Home Office. ®