This statement or claim is extremely FALSE.
What they should have stated is that Linux can’t get infected by WINDOWS Viruses. Linux actually does have a few thousand written viruses and worms that can damage your system. Although they are rarely seen on regular consumer systems at home. ClamAV for axample, works well to detect Linux and Unix malware.

Long story, short….
Never let anyone tell you that your Operating System is completely immune from malicious code. Linux is an OS. Sombody somwhere on the planet has written something malicious for it to serve their own twisted means.
Always use a well configured Firewall and always use AntiVirus software. DON’T Forget to UPDATE IT OFTEN.