If you've heard "2SZ" on the HF bands, it's not a pirate. The call sign is part of a special event
http://www.gb2nz.com/ to mark the 90th anniversary of the first Amateur Radio contact between Great Britain and New Zealand in 1924. The radio operator in England was 18-year-old Cecil Goyder, operating the Mill Hill School station 2SZ.
The Radio Society of Great Britain, in partnership with groups of amateurs in the UK and New Zealand, invited participation in the celebration by recreating that original contact between the UK and New Zealand on 80 meters, and a lot of the activity has concentrated on that band when propagation has been favorable. The 2SZ call sign joined special event station GB2NZ, operated by various groups, in the celebration, which wraps up in the UK on October 18, the actual anniversary date.
On the New Zealand end of the circuit, ZM90DX
http://www.zm90dx.com/ and ZL4AA are on the air, with many individual ZL stations also participating. ZM90DX will be active until October 31. Kiwi sheep farmer Frank Bell, Z4AA, a World War I veteran, was the other operator for the historic October 18, 1924 contact. Amateur Radio had only been authorized a year earlier in New Zealand, and Bell already had set some distance records. These included a September 21, 1924, contact with U6BCP in California, and an October 13, 1924, contact with U1SF in Connecticut.
In later years, Goyder emigrated to the US, where he served as the first communications officer for the United Nations. As for Bell, after being elected in absentia to the executive committee of the new International Amateur Radio Union in 1925, he apparently lost interest in radio. His sister Brenda took over Z4AA to become New Zealand's first female Amateur Radio operator and was the first New Zealand ham to contact South Africa in 1927. She later became a radio broadcaster.
1st G > ZL Contact