Question: The authors further explore several possible approaches using what?
Evidence: Internet “trolls” are users of an online community who quarrel and upset people, seeking to sow discord by posting inflammatory content. More recently, organized “troll farms” of political opinion manipulation trolls have also emerged.
Such farms usually consist of state-sponsored agents who control a set of pseudonymous user accounts and personas, the so-called “sockpuppets”, which disseminate misinformation and propaganda in order to sway opinions, destabilize the society, and even influence elections BIBREF0.
The behavior of political trolls has been analyzed in different recent circumstances, such as the 2016 US Presidential Elections and the Brexit referendum in UK BIBREF0, BIBREF1. However, this kind of analysis requires painstaking and time-consuming manual labor to sift through the data and to categorize the trolls according to their actions. Our goal in the current paper is to automate this process with the help of machine learning (ML). In particular, we focus on the case of the 2016 US Presidential Elections, for which a public dataset from Twitter is available. For this case, we consider only accounts that post content in English, and we wish to divide the trolls into some of the functional categories identified by BIBREF0: left troll, right troll, and news feed.
We consider two possible scenarios. The first, prototypical ML scenario is supervised learning, where we want to learn a function from users to categories {left, right, news feed}, and the ground truth labels for the troll users are available. This scenario has been considered previously in the literature by BIBREF2. Unfortunately, a solution for such a scenario is not directly applicable to a real-world use case. Suppose a new troll farm trying to sway the upcoming European or US elections has just been discovered. While the identities of the accounts might be available, the labels to learn from would not be present. Thus, any supervised machine learning approach would fall short of being a fully automated solution to our initial problem.
A more realistic scenario assumes that labels for troll accounts are not available. In this case, we need to use some external information in order to learn a labeling function. Indeed, we leverage more persistent entities and their labels: news media. We assume a learning scenario with distant supervision where labels for news media are available. By combining these labels with a citation graph from the troll accounts to news media, we can infer the final labeling on the accounts themselves without any need for manual labeling.
One advantage of using distant supervision is that we can get insights about the behavior of a newly-discovered troll farm quickly and effortlessly. Differently from troll accounts in social media, which usually have a high churn rate, news media accounts in social media are quite stable. Therefore, the latter can be used as an anchor point to understand the behavior of trolls, for which data may not be available.
We rely on embeddings extracted from social media. In particular, we use a combination of embeddings built on the user-to-user mention graph, the user-to-hashtag mention graph, and the text of the tweets of the troll accounts. We further explore several possible approaches using label propagation for the distant supervision scenario.
As a result of our approach, we improve the classification accuracy by more than 5 percentage points for the supervised learning scenario. The distant supervision scenario has not previously been considered in the literature, and is one of the main contributions of the paper. We show that even by hiding the labels from the ML algorithm, we can recover 78.5% of the correct labels.
The contributions of this paper can be summarized as follows:
We predict the political role of Internet trolls (left, news feed, right) in a realistic, unsupervised scenario, where labels for the trolls are not available, and which has not been explored in the literature before.
We propose a novel distant supervision approach for this scenario, based on graph embeddings, BERT, and label propagation, which projects the more-commonly-available labels for news media onto the trolls who cited these media.
We improve over the state of the art in the traditional, fully supervised setting, where training labels are available.
We further explore several possible approaches using label propagation for the distant supervision scenario.
Answer: Label propagation for the distant supervision scenario.