BEIJING • China has urged Windows users to protect themselves against a new ransomware virus similar to the "WannaCry" bug that wreaked havoc worldwide last week.

"UIWIX" encrypts and renames files through a bug in the Windows operating system, China's National Computer Virus Emergency Response Centre (CVERC) warned in a public announcement on Wednesday, telling users to install the latest Microsoft update.

The warning comes on the heels of the "WannaCry" cyber attack, which has hit hundreds of thousands of computers worldwide.

While no UIWIX infections have yet been detected in China, the virus has spread in other countries and prompted a security alert last week from the Danish cyber-security company Heimdal Security.

"UIWIX ransomware is picking up where the first WannaCry wave left off, without a kill switch domain and the same self-replicating abilities that enable it to spread fast," the firm said in a statement.

Global cyber-security firm Proofpoint warned on Wednesday about another large-scale, stealthy cyber attack linked to WannaCry called Adylkuzz.

Proofpoint said the attack by Adylkuzz could grow to become far larger than last week's assault on computers worldwide. The new attack targets the same vulnerabilities the WannaCry ransomware worm exploited but, rather than freeze files, uses the hundreds of thousands of computers believed to have been infected to "mine" virtual currency. It does this in the background, without crippling the computer.

It mines the virtual currency, Monero, and transfers the money created to the authors of the virus.

Virtual currencies such as Monero and bitcoin use the computers of volunteers to record transactions. They are said to mine for the currency and are occasionally rewarded with a piece of it.

Proofpoint said in a blog that symptoms of the attack include loss of access to shared Windows resources and degradation of PC and server performance, effects which some users may not notice immediately.

AGENCE FRANCE-PRESSE