Online content creators spend significant time and effort building their user base through a long, often arduous process that requires finding the right "niche" to cater to. So, what incentive is there for an established content creator known for cat memes to completely reinvent their channel and start promoting cryptocurrency services or covering electoral news events? We explore this problem of repurposed channels, whereby a channel changes its identity and contents. We first characterize a market for "second-hand" social media accounts, which recorded sales exceeding USD 1M during our 6-month observation period. Observing YouTube channels (re)sold over these 6 months, we find that a substantial number (53%) are used to disseminate policy-sensitive content, often without facing any penalty. Surprisingly, these channels seem to gain rather than lose subscribers. We estimate the prevalence of repurposing using two snapshots of ~1.4M YouTube accounts sampled from an ecologically valid proxy. In a 3-month period, we estimate that ~0.25% channels were repurposed. We experimentally confirm that these repurposed channels share several characteristics with sold channels -- mainly, they have a significantly high presence of policy-sensitive content. Across repurposed channels, we find channels similar to those used in influence operations, as well as channels used for financial scams. Repurposed channels have large audiences; across two observed samples, repurposed channels held ~193M and ~44M subscribers. We reason that purchasing an existing audience and the credibility associated with an established account is advantageous to financially- and ideologically-motivated adversaries. This phenomenon is not exclusive to YouTube and we posit that the market for cultivating organic audiences is set to grow, particularly if it remains unchallenged by mitigations, technical or otherwise.

翻译：在线内容创作者需通过漫长且往往艰辛的过程，投入大量时间与精力来构建用户基础，这一过程需要找到合适的“利基”领域以满足受众需求。那么，一个以发布猫咪表情包而闻名的成熟内容创作者，为何会彻底重塑其频道并开始推广加密货币服务或报道选举新闻事件？我们探讨了这种频道用途变更的现象，即频道改变其身份与内容。我们首先描述了“二手”社交媒体账户市场的特征，在为期六个月的观察期内，该市场记录的交易额超过100万美元。通过对这六个月期间（转）售的YouTube频道进行观察，我们发现其中大量频道（53%）被用于传播政策敏感性内容，且往往未受到任何处罚。令人惊讶的是，这些频道的订阅者数量似乎不降反增。我们通过从生态有效的代理样本中抽取约140万个YouTube账户的两个快照，估算了频道用途变更的普遍程度。在三个月期间，我们估计约有0.25%的频道发生了用途变更。我们通过实验证实，这些用途变更的频道与已售出的频道具有若干共同特征——主要表现为政策敏感性内容的占比显著偏高。在用途变更的频道中，我们发现了类似于影响力操作中使用的频道，以及用于金融诈骗的频道。用途变更的频道拥有庞大受众；在两个观测样本中，这些频道分别持有约1.93亿和约4400万订阅者。我们认为，购买现有受众及成熟账户所关联的信誉，对于受经济利益和意识形态驱动的攻击者具有优势。这一现象并非YouTube独有，我们推断培育有机受众的市场将持续增长，尤其是在缺乏技术或其他层面缓解措施的情况下。