they turned up in Australia last month ... The organisation said seeds of unknown origin pose a major threat to Australia’s biosecurity and could introduce invasive species and pests to Australia’s ecosystem ... American Agriculture officials believe the seeds are part of an e-commerce "brushing" scam. Under the scheme, e-commerce sellers boost their ratings on sites like eBay and Amazon by creating fake orders - sending unsolicited items to random addresses to artificially boost sales and fabricate customer reviews.