Social platforms such as Twitter are increasingly threatened by automated social bots, which can manipulate public opinion, spread misinformation, and compromise platform integrity. To detect such accounts, various methods have been proposed, with many recent approaches leveraging graph neural networks (GNNs) due to their ability to model relational structures among users. However, these models may be vulnerable to adversarial perturbations that exploit their structural dependencies. To investigate this vulnerability, we propose a targeted black-box node injection attack that deceives detection models by injecting a new bot near a target bot, causing both to evade detection. This attack is specifically designed to exploit GNN-based model behaviors and does not require any access to model parameters or architecture. Given the success of this attack in exposing structural weaknesses, it is essential to develop effective defenses to improve the robustness of detection models. To this end, we introduce a cost-efficient adversarial training method with reweighted supervision, which selectively emphasizes adversarial samples during learning. This approach improves model robustness without increasing computational cost or requiring additional data. The effectiveness of our attack and defense methods is demonstrated through experiential evaluations conducted on six different models. Specifically, we achieve a maximum attack success rate (ASR) of 95.74% and robustness improvement of 95.74% in Cresci-2015 and achieve a maximum ASR of 97.15% and robustness improvement of 56.20% in TwiBot-22. The detection performance of the models fluctuates less than 2% after adversarial training.

News captioning aims to describe an image with its news article body as input. It greatly relies on a set of detected named entities, including real-world people, organizations, and places. This article exploits commonsense knowledge to understand named entities for news captioning. By “understand,” we mean correlating the news content with commonsense in the wild, which helps an agent to (1) distinguish semantically similar named entities and (2) describe named entities using words outside of training corpora. Our approach consists of three modules: (a) Filter Module aims to clarify the commonsense concerning a named entity from two aspects: what does it mean ? and what is it related to ?, which divide the commonsense into explanatory knowledge and relevant knowledge , respectively. (b) Distinguish Module aggregates explanatory knowledge from node-degree , dependency , and distinguish three aspects to distinguish semantically similar named entities. (c) Enrich Module attaches relevant knowledge to named entities to enrich the entity description by commonsense information (e.g., identity and social position). Finally, all of information is integrated into the large multimodal model to generate the news caption. Extensive experiments on two challenging datasets (i.e., GoodNews and NYTimes) demonstrate the superiority of our method. Ablation studies and visualization further validate its effectiveness in understanding named entities.